Other animals use them for digging, scratching or fighting, but we don't. They're useless but at the same time they don't distract from the business of living. Pigeons and a couple of species of fish do something similar to suckling their young, a task they split down the middle. Discus and orange chromide fish feed their young with a nutritious mucus from the sides of their bodies. Milk isn't sweat.
Male humans look pretty unhelpful next to pigeons.
If men would just submit themselves to an intense barrage of hormone therapy, affecting every organ system of the body in unknown ways, maybe they would be able to suckle their young and throw off the charge of reptilianism once and for all. It seems unlikely. They've managed to hang in there all these millennia, and many guys speak well of their nipples and would clearly vote to retain them. Ask any boar hog and he'll tell you the same. The Emotional Lives of Animals.