For thousands of years, buttocks were the primary sexual “presentation” for humans, as it is for all the rest of the higher primates. It is only in the last 150 years or so that interest has moved from the buttocks to the breast, and it’s no coincidence that this also marks the start of the Industrial Revolution. As women entered the workforce, bottle-feeding became the norm rather than the exception. Never being properly weaned, children – both male and female – acquired lifelong oral fixations, resulting in, for example, the growth of cigarette smoking on a massive scale.
I had a friend who identified as hetersosexual, but she would often sleep with women because she had a fetish for breasts, and the only way she could get access to them was to sleep with the women who had them. (She explained that it’s just not polite to play with a woman’s boobies and then go home.) I suspect that there are quite a few women out there like my friend who, as a result of their oral fixations, find themselves with a seemingly bizarre attraction to breasts without any concommitant attraction to the sexual organs of a woman.