Excellent question @kindabella. Baking for lo-poly purposes is arguably the most common reason for baking. But for me, as you hinted, I like to use bake data to assist my texture painting. I find that it helps unify the details between geometry and texture.
Personally I don’t use AO for rendering anymore, as in an AO pass. It was good a decade ago when global illumination took too long to render – AO got us half-way toward more realistic lighting. But by nature, it’s unrealistic by itself. However it works great as a utility for painting texture detail in crevices. Displacement is also helpful in a similar way, to add emphasis to the diffuse texture’s divots and bumps.
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