The cleavage of the breasts also looks very much like the cleft at the top of the ass. When humans began to walk upright, a woman’s ass was no longer as prominent in its presentation. This led to the development of larger tits to act as frontal display. Basically they’re an ass a woman carries on her chest- and it’s absolutely not an accident they give you a boner. Feeding children is an equally important task, but the shape of the human breast has nothing to do with that. They’d serve that purpose even if they were flat like a chimp’s tits.
Many body parts serve dual, equally important functions- like your dick, it’s a sewer pipe that you also fuck with.