Why Only Sattvik.? Only Bhagawan Shiva is glorified in all 18 puranas under various names.
Sri Skanda Purana 1.1.1.:
Lomaśa said:
13. In all the eighteen Purāṇas, Only Śiva is sung about as the greatest (lord). Hence no one is competent to recount the greatness of Śiva (adequately).
14. Heaven and liberation (from Saṃsāra) will be attained by those people who repeatedly utter the two-syllabled name Śi-va.[8] Not otherwise.
15. Munificent indeed is Mahādeva, (the great god), the lord of Devas, the Supreme Ruler. Since everything has been given by him, he is named Sarva.
Atharva Veda 15.6.:
स बृहतीं दिशमनु व्यचलत्। तमितिहासश्च पुराणं च गाथाश्च नाराशंसीश्चानुव्यचलन् । इतिहासस्य च वै स पुराणस्य च गाथानां च नाराशंसीनां च प्रियं धाम भवति य एवं वेद ॥४॥
4. He (Shiva) went away to the great region. Itihāsa and Purāna and Gāthās and Nārāsansis followed him. He who, etc.
Shiva Sankalpa Upanishad.:
च॒तुरो॑ वे॒दान॑धीयी॒त॒ स॒र्वशा᳚स्त्रम॒यं विदुः॑ ।
इ॒ति॒हा॒सपु॑राणा॒नां तन्मे॒ मनः॑ शि॒वसं॑क॒ल्पम॑स्तु ॥
He (Shiva) as the four Vedas, Itihāsa, and the Purāṇas are known to be the source of all scriptures or knowledge; may my mind aspire towards Lord Śiva (or) Auspicious Śiva thoughts.
Let me give examples from Sri Vishnu Puran itself.:
As we all know.:
Adhyaya 1 Pada 3 of Purva Mimamsa Sutras of Jaimini discuss of Authority of Shruti and Smriti and Authority of Shruti being higher than Smriti.
Adhikarana 2 states.:
Shruti (Veda) more authoritative than Smrti.
Sutra 3 of Adhikarana 2 states.:
When There Is Conflict (Between Veda and Smriti,) The Smriti Should Be Disregarded; Because It Is Only When There Is No Such Conflict That There Is An Assumption (Of Vedic Text In Support Of Smriti).
The following verse from Vishnu Purana esoterically states that entire creation is Vishnu that is why he is the creator, he gets created, he is the protector, he gets protected, and he is the destroyer, he gets destroyed.
"sa eva srujyah sa cha sargakartAh | sa eva pAlyanti cha pAlyate cha | brahmAdyavastHabHirsHEshamUrtir | vishNurvarishTHo varado varENyah |" (Vishnu Purana 1:2:70).
"That god who is present in every form, who is the best and giver of boons, who is worthy of worship, that god Vishnu only creates as Brahma and he himself gets created, he alone protects and he is the one who gets protected, and he alone destroys everyone and it is again he alone who gets destroyed".
It further says that whatever exists and doesn’t exist everything is Hari.
“sUryadayO grahastArA nakshatrANyakHilam jagat |
mUrtAmUrtamadrushyam cha drushyam cha purushOttama |
yadyOktam yadya navivOktam mayAtra paramEshwara |
tatsarvam twam namastubhyam bhUyO bhUyO namonamah |" (Vishnu Purana 1:4:23(b)-24).
“[O Hari] Thou art the sun, the planets, the stars, constellations, and entire universe are you alone. O Purushottama! O Parameshwara! the manifest, unmanifest, visible, invisible and everything that I said and everything that i didn't say about you everything is you alone. Salutations to you who are such, Salutations!”
Shruti.:
"vishvam bhutam bhuvanam citram bahudha jatam jayamanam cayat |
sarvo hyesha rudrastasmai rudraya namo astu |" (Yajurveda Taittiriya Aranyaka 10:24:1).
"The whole universe, the created beings and whatever there is manifoldly and profusely created in the past and in the present in the form of the world, all that is indeed this Rudra. Salutations be to Rudra who is such".
"Yo rudro agnau yo apsu ya oshhadhishhu | Yo rudro vishva bhuvanaaavivesha tasmai rudraya namo astu |" (Yajurveda Taittiriya Samhita 5.5.9.3).
"That Rudra who has even entered into and pervaded fire, the waters, vegetation, and all the worlds, let my salutations be to that Rudra".
Vishnu Purana states the following in chapter two.
“pradhAnapurushavyaktakAlAnAm paramam hi yat |
pashyanti sUrayah shuddham tadvishNOh paramam padam |" (Vishnu Puran 1:2:16).
"That Supreme Being transcends pradhana (lower form of Prakriti), purusha (all living beings), vyakta (manifest), and kala (time), and that place which is visible only to the learned yogis is called as the lofty station of Vishnu".
Shruti.:
“athaanyatraapyuktam.h: yathaa vaapsu chaariNaH shaakunikaH suutrayantreNoddhR^ityodare.agnau juhotyeva.n vaa va khalvimaanpraaNaanomityanenoddhR^ityaanaamaye.agnau juhoti atastaptorvivaso.atha yathaa taptorvi saarpistR^iNakaaShThasa.nsparshenojjvalatiityeva.n vaa va khalvasaavapraaNaakhyaH praaNasa.nsparshenojjvalati atha yadujjvalatyetadbrahmaNo ruupa.n chaitadviShNoH paramaM padam.h chaitadrudrasya rudratvametattadaparimitadhaa chaatmaana.n vibhajya puurayatiimaa.n lokaanityeva.n hyaaha vahneshcha yadvatkhalu visphuli~NgaaH suuryaanmayuukhaashcha tathaiva tasyapraaNaadayo vai punareva tasmaad abhyuchcharantiiha yathaakrameNa |” (Maitrayani Upanishad 6:26).
“And thus it has also been said elsewhere: As a sportsman, after drawing out the denizens of the waters with a net, offers them (as a sacrifice) in the fire of his stomach, thus are these Prânas (vital airs), after they have been drawn out with the syllable Om, offered in the faultless fire (Brahman). Hence he is like a heated vessel (full of clarified butter); for as the clarified butter in the heated vessel lights up, when touched with grass and sticks, thus does this being which is called Not-breath (Âtman) light up, when touched by the Prânas (the vital airs). And that which flares up, that is the manifest form of Brahman, that is the highest place of Vishnu; that is the essence of Rudra. And this, dividing his Self in endless ways, fills all these worlds. And thus it is said: 'As the sparks from the fire, and as the rays from the sun, thus do his Prânas and the rest in proper order again and again proceed from him here on earth.'”
“maayaa.n tu prakR^iti.n vidyaanmaayina.n cha maheshvaram.h | tasyavayavabhuutaistu vyaapta.n sarvamida.n jagat.h |” (Swetasvatara Upanishad 4:10).
“Know then Prakriti (nature) is Mâyâ , and the Maheshwara the Mâyin; the whole world is filled with what are his members (forms)”.
"kṣaraṃ pradhānam amṛtākṣaraṃ haraḥ kṣarātmānāv īśate deva ekaḥ | tasyābhidhyānād yojanāt tattvabhāvād bhūyaś cānte viśvamāyānivṛttiḥ ||" (Swetasvatara Upanishad 1:10).
"Prakriti (Pradhana) is perishable. Hara, the Lord, is immortal and imperishable. The non-dual Supreme Self rules both prakriti and the individual soul. Through constant meditation on Him, by union with Him, by the knowledge of identity with Him, one attains, in the end, cessation of the illusion of phenomena."
Vishnu Puran.:
"tatastu tatparambrahma paramAtmA jaganmayah | sarvagah sarvabhUtEshah sarvAtmA paramEshwarah | pradhAnapurushO vApi pravishyAtmEchHayA harih |
kshobhayamAsa samprAptE sarvakAlE vyayAvyayO |" (Vishnu Purana 1:2:28-29).
"Then that supreme brahman, the supreme soul of universal form, who is all pervading, who is lord of all creatures, who is the soul of all beings, - that Parameshwara by his will entered into the Pradhana (lower prakriti) and Purusha (all entities having conciousness) and agitated them".
"srisHtistHityantakaraNI brahmavishnushivAtmikAm |
sa sangyAm yAti bhagavAnEka eva janArdanah |" (Vishnu Purana 1:2:66).
"That god Janardana alone assumes the forms of Brahma, Vishnu and Rudra (destroyer deity) for the tasks of creation, maintenance and destruction".
Shruti.:
Shiva menifestation as Brahma.:
“sá yát sárvān antardeśā́n ánu vyácalat parameṣṭhī́ bhūtvā́nuvyàcalad |” (Atharva Veda XV:14:12).
“He (Vratya-Shiva), when he went away to all the intermediate spaces, went away having become Parameshthin and having made Devotion an eater of food”.
Shiva manifested Vishnu from himself.
“sá yád dhruvā́ṃ díśam ánu vyácalad víṣṇur bhūtvā́nuvyàcalad|” (Atharva Veda XV:14:5).
“He, when he went away to the stedfast region, went away having become Vishnu”.
Shiva became Rudra (the deity responsible for destruction – kAlAgni rudrA).:
“sá yát paśū́n ánu vyácalad rudró bhūtvā́nuvyàcalad óṣadhīr annādī́ḥ kr̥tvā́ |” (Atharva Veda XV:14:6).
“He, when he went away to animals, went away having become Rudra and having made herbs eaters of food”.
Atharva Shiras Upanishad 5.2 and Svetasvatara Upaniṣhad 3.2 says thus.:
एको हि रुद्रो न द्वितीयाय तस्थुर्य इमांल्लोकानीशत ईशनीभिः। प्रत्यङ्जनांस्तिष्ठति सञ्चुकोचान्तकाले संसृज्य विश्वा भुवनानि गोपाः॥
“Rudra is truly the only one; for the knowers of Brahman do not admit the existence of any second being, He Ishana, alone rules all the worlds by His powers (as Indra). He dwells as the inner Self (Atman) of every living beings. After having created all the worlds (as Brahmā), He, their Protector (as Vishnu), takes them back into Himself at the end of time (as Kāla, by giving them Kaivalyam Moksham)."
“Namo bhavaya cha rudraya cha | namah sharvaya cha pashupataye cha |” (Yajurveda Sri Rudram- Anuvaka 5).
“Salutations to Rudra who is the source of all things (Bhava) and to Him who is the destroyer of all ills (Rudra). Salutations to the destroyer of everything (Sharva) and to the protector of all beings in bondage (Pashupati)”.
Look at at this interesting verse. It says all males are the forms of Vishnu and all females are the forms of Lakshmi.
“kim chAtibahunOktEna sankshEpENEdamuchyatE |
dEvatiryakmanushyAdOu punnAmA bhagawAn harih |
strInAmnI shrIshcha vigyEyA nAnayOrvidhyatE param |”(Vishnu Purana 1:8:34-35).
“What else can I tell you about their forms? In summary, among all the deities, creatures and humans, all the beings of masculine gender are Hari’s forms and all the beings of feminine forms are Lakshmi’s forms. There is nothing else in this world apart from these two”.
Shruti.:
“pu.nli~Nga.n sarvamiishaana.n striili~NgaM bhagavatyumaa |
umaarudraatmikaaH sarvaaH grajaaH sthaavaraja~NgamaaH |” (Rudra hridayopanishad 1:9-10).
“The masculine gender is Lord Siva. The feminine gender is Sri Bhavani Devi. All the mobile and immobile creation of this universe is filled up with Uma and Rudra”.
Shruti (Upanishad) says,
“rudro.artha aksharaH somaa tasmai tasyai namo namaH |” (Rudra hridayopanishat 1:23a).
“Rudra is the meaning and Uma is the word, prostrations to him and her”.
Vishnu Purana applies the same and says,
“arthO vishNuriyam vANI |” (Vishnu Purana 1:8:18b).
“Vishnu is the meaning and Lakshmi is the word”.
Shruti (Upanishad) says,
“rudro vahnirumaa svaahaa tasmai tasyai namo namaH |” (Rudra hridayopanishat 1:21a).
“Rudra is Agni and Uma is Swaha, prostrations to him and her”.
Vishnu Purana applies the same and says,
“swahA lakshmIrjagannAthO vAsudEvO hutashanah | (Vishnu Purana 1:8:22b).
“Lakshmi is Swaha and lord of the world viz. Vasudeva is Agni”.
Shruti (Upanishad) says the following which is correct as per Vedas and we analyzed this in detail.
“rudro vishhNurumaa lakshmiistasmai tasyai namo namaH |” (Rudra hridayopanishat 1:18b).
“Rudra is Vishnu and Uma is Lakshmi, prostrations to him and her”.
Vishnu Purana modifies the same mythically and says,
“shankarO bhagawAnchHourIgourI lakshmIrdwijottama |” (Vishnu Purana 1:8:23a).
“O best of the brahmana! Vishnu is Shankara and Lakshmi is Gowri”.
Shruti (Upanishad) says,
“rudraH suurya umaa chhaayaa tasmai tasyai namo namaH |” (Rudra hridayopanishat 1:19a).
“Rudra is Sun and Uma is dawn, prostrations to him and her”.
Vishnu Purana applies the same and says,
“maitrEya kEshavah sUryastatprabhA kamalAlayA |” (Vishnu Purana 1:8:23b).
“O Maitreya! Keshava is the sun and lotus goddess Kamala is the Dawn”.
Shruti (Upanishad) says,
“rudraH soma umaa taaraa tasmai tasyai namo namaH |” (Rudra hridayopanishat 1:19b).
“Rudra is Moon and Uma is Tara, prostrations to him and her”.
Vishnu Purana applies the same and says,
“shashAnkah shrIdharah kAntih shrIshthaivAnapAyinI |” (Vishnu Purana 1:8:24a).
“Vishnu is the moon and Lakshmi is the light (symbolic of Tara/Star).”
Shruti (Upanishad) says,
“rudro vR^iksha umaa vallii tasmai tasyai namo namaH |” (Rudra hridayopanishat 1:22a).
“Rudra is the tree and Uma is the creeper, prostrations to him and her”.
Vishnu Purana applies the same and says,
“latAbhUtA jaganmAtA shrIvishNurdrumasangitah |” (Vishnu Purana 1:8:30b).
“Vishnu is the tree and Lakshmi is the creeper”.
Shruti (Upanishad) says,
“rudro divaa umaa raatristasmai tasyai namo namaH |” (Rudra hridayopanishat 1:20a).
“Rudra is the day and Uma is the night, prostrations to him and her”.
Vishnu Purana applies the same and says,
“vibhAvarI shrIrdivasO dEvaschakragadAdharah |” (Vishnu Purana 1:8:31a).
“Vishnu is the day and Lakshmi is the night”.
Finally, the crux of the analysis is summed up by Shruti in the below verse very clearly. It clearly says that those who worship Vishnu are actually worshiping Shiva. It also warns people saying that those who hate Mahadeva are hating Vishnu.
“ye namasyanti govinda.n te namasyanti sha~Nkaram.h |
ye.archayanti hariM bhaktyaa te.archayanti vR^ishhadhvajam.h |
ye dvishhanti viruupaaksha.n te dvishhanti janaardanam.h |
ye rudra.n naabhijaananti te na jaananti keshavam.h |” (Rudra Hridayoanishat 1:6-7).
“Those who adore Govinda, are adoring Sankara. They, who worship Hari with devotion, are worshipping the bull-bannered deity in reality. Those who hate the three eyed lord, they are hating Janardana, and those who do not understand Rudra do not understand Kesava”.
So, it's quite evident that Sage Parashara sung the glories of Shiva-Shakti under the names of Lakshmi -Narayana.
Conclusion.: Thus, in same way other puranas also does the same. Because YajurVeda clearly says that it is Rudra who is the indweller of all the gods - Yajurveda (IV:5:9:p) which states, “devana hridayebhyo namah”, which means, “salutations to the Lord Rudra who is the indweller of hearts of all the gods”.
I hope this clarifies all the queries. Prd..