It is said that When Shahaji died, Jijabai tried to commit sati - committing suicide by burning oneself in the husband's pyre, but Shivaji stopped her from doing so by his request. Why did he not ban the Sati custom altogether in his kingdom?
Shivaji appears to have followed orthodox Hinduism so banning satī outright would go against the kṣatriya code.
For the lives of the Bhagwat saints were full of gentleness and love. Theirs was a catholic generosity and toleration. In their hearts was no room for pride or hatred. A religion that consistently identified Ram with Rahim could admit of no parochial or even national patriotism in religion. Nor is there any evidence to show that Shivaji himself was an active propagator of this Vaishnav cult. His faith was deeply rooted in the Sanatan Dharma, with the result that, to the moment of his death, his simple piety and faith in the goddess Bhavani never faltered or forsook him. If he did instill in his followers and supporters a passionate love of religion along with the worship of liberty, it was not by any means with any material aid of the Vaishnav or Bhagwat Dharma. The religious love and pride he inculcated in them was the love of the orthodox or Sanatan Dharma, with its belief in the sanctity of kine and Brahmans, its injunctions for the observance of caste distinctions, its recognition and encouragement of idol worship, and its exhortation urging the value and necessity of all ceremonial usages. And it cannot be disputed that the conduct of Shivaji himself personally and that of most of his followers was in full accord with the precepts of the orthodox religion, inasmuch as in none of the extant bakhars is there the least evidence to the contrary.
Also, if Shivaji was against the idea of satī he would have at least made sure none of his wives committed satī after his death but then one of his childless wives, Putlabai, did commit satī:
The death of the great leader was a grievous blow to the ministers and nobles of the state and the relations of the royal family. All classes of society mourned the loss. The ministers took the precaution to close the castle gate and prevent the publication of the tragic news. The funeral of the great king was celebrated with royal pomp and honours. The third wife of Shivaji, Putlabai, performed the sati rite upon the funeral pyre of her husband. The obsequies were performed by a member of the Bhonsle House, Sabaji Bhonsle of Shingnapur, assisted by Prince Kajaram, the latter being too young to perform all the rites himself. Religious charities in honour of the event were dispensed on a liberal scale.
Shivaji married seven wives. Sayibai, the mother of Sambhaji came of the Nimbalkar family; Soyerabai the mother of Rajaram was a daughter of the Shirke family. Putlabai, the third wife, who performed the sati rite on the death of Shivaji, had no issue. The fourth wife Sakwarbai came of the Gaikwar family. She gave birth to Kamaljabai, who was married to Janoji Palkar...
And the main reason why Shivaji's mother Jijabai stopped short of committing satī was that Shivaji was deeply attached to her and Shivaji's ministers thought her demise would indirectly contribute to the downfall of the empire.
Jijabai was more disconsolate still her grief it was impossible to calm or restrain. She prepared to perform the rite of sati, with the devotion of a faithful Kshatriya wife. This resolution of his mother aggravated Shivaji's sorrow. He begged her, besought her, held fast to her feet, but she would not yield. The ministers of state, Moropant, Niraji, Dattaji and others at length intervened representing to Jijabai that Shivaji would so much take to heart her self-immolation by the act of sati as scarcely to outlive her death and the empire he had built up by long years of labour was sure to collapse with his death. The name of Shivaji and together with it that of Shahaji would both alike be extinguished with her death. It was, therefore, imperative in the interests of the state that she should bear her grief in silence and patience instead of yielding to the impulsive thought of sacrificing herself on her husband's funeral pyre. This weighty argument shook her resolution. In order that she might witness the glory of her son she consented to live a widowed life.
Shivaji performed his father's funeral rites in the orthodox Hindu fashion, spending lakhs of rupees that the hero's shade might rest in peace...