system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why do guys like boobs?

I know not everyone likes the same size of boobs. and I'm sure there are some guys out there that don't like boobs. But in my experience we males typically like boobs. Why is this? Is there some kind of evolutionary advantage that certain size boobs have over other boobs? Or is it just a convenient place to have a fat deposit?
gpt
Back when we were walking like apes on all fours, we could easily look at each other's butt, and judge the fertility, but once we started to walk upright, it wasn't in plain view anymore, so we started selecting based on what we could see instead. Breasts are a nice indicator for fertility, because they promise more milk for the baby and fat storage, so the females evolved to always have large breasts, instead of only during pregnancy like other mammals.

So boobs are basically a replacement butt. We still like butts, though, because nature never cleans up old code.