Bhakti is one of the ways in developing an inclination towards the God, whereas the REALISATION stage of the sages like Sri Ramana Maharshi is the final stage.
Many saints, who started in Bhakti marga, finally ended in SELF REALISATION. Yogi Ramaiah, Saint Namadev, etc, are a few such people quoted for illustration purpose.
Saint Namadev was a devotee ...
The question, why one worships Ishwara, is answered by Krishna (and commentators) in bhagavad geeta 7.16.
caturvidhā bhajantē māṅ janāḥ sukṛtinō.rjuna.
ārtō jijñāsurarthārthī jñānī ca bharatarṣabha৷৷7.16৷৷
English Translation By Swami Gambirananda
7.16 O Arjuna, foremost of the Bharata dynasty, four classes of people of virtuous ...