What is the purpose for which the Lord takes birth in a human form?

God incarnates not merely for the destruction of the wicked; that’s just an excuse, one of the obvious reasons. Really speaking, God incarnates for the sake of faithful devotees. The cow has milk primarily as sustenance for its calf. But it’s used by man for maintaining his health. So too, God incarnates primarily for the sustenance of the faithful, devoted, virtuous, and good. But even faithless and bad use the chance for their own purpose. Therefore, in Bhagavata, stories of such wicked persons intervene amidst accounts of the glory and grace of God. This doesn’t make the Bhagavata any less holy. When sweet juice has been squeezed out of the sugarcane, the bagasse is left over and discarded! When the sweetness of divine majesty has been tasted, the bagasse can be thrown out. The cane has both bagasse and sugar; it cannot be only sugar. So too, devotees must be amidst the faithless; there cannot be one without the other.

– Bhagavatha Vahini, Ch 28.