a good angle on the question is, why are men so attracted to women’s breasts?
that men have “breasts” is an evolutionary artifact. a man’s breasts are the undeveloped zygote equivalent to a woman’s breasts, just as a woman’s clitoris is the undeveloped zygote equivalent to a man’s penis.
a theory regarding male attraction to female breasts is that as humans evolved from quadrupedal to bipedal, attraction to the cleavage of a female’s butt was replaced by attraction to the cleavage of a female’s breasts.
as quadrupeds, sexual intercourse was oriented from the rear of the female. as bipeds, intercourse was oriented from the front of the female. hence, breast cleavage replaced butt cleavage as a sexual attraction for males to females.