I think it just goes back to two main things. Being breast fed as a child, you grow to depend and love on the boob, so it’s kind of baked into our genetics to some degree. Secondly the Church basically sexualized boobs and are considered taboo private parts most people aren’t supposed to see so that gives it some sort of allure that you’re seeing something your not supposed to, which in American culture is pretty much the norm. Think of how ankles were such a thing to flaunt not that long ago at all. Some cultures just outright don’t care about boobs and just let em hang out so I really just feel like it boils down to culture for most of it.

Past all of that, and personally, a nicely resting boob is just a great sight. Something about the curves and seeing the body in its natural form idk. Also, squishy, they’re great to just have a hand on and give a good squish every now and then.