Breasts are a secodary sex organ. And i dont know how you prefer your intercourse, but i happily fondle with the breasts of my wife during sex. If you break down sex to just reproduction, ofc they are only needed to feed the baby. But culturally the are sexual organs and erotic. So its normal in my (european) culture to hide breasts (at least the nipples) from public.

Edit: I would like to add that its not okay to demonetize Naomi Wus 3D Bust Video. Thats another discussion and i think we are on par here.