Why are breasts so sexualized?

If breasts are not sex organs and they exist, just like in other animals, to feed babies, why are they so hypersexualized? I believe in the past, ancient women did not need to cover up their breasts. When a woman in public breastfeeds, why is it seen as gross and something that should be hidden? No woman is trying to flash herself, just trying to feed her baby, and even if she covers her breasts to breastfeed, why is still seen as taboo? And one last question, why is is okay for a man to not cover his chest but it's not okay for a woman to not wear anything covering her chest? Are breasts really that taboo?