 They typically look different between women and men, though not in all cases. But all members of the human species have breasts. That's why men can even get breast cancer. It's rare, but it does happen because men have breasts. So even if you were trying to include men in breastfeeding, there's no reason to change the word breast. Men have those. It's the feeding part that complicates matters. In a similar fashion, all women have chests.