They are not actually made for children.

If they were, all mammals would have boobs. But only human females do. The other develop during pregnancy and remove them after.

But humans have uniquely expensive children, putting uniquely hard pressures on both parties.

The female must choose the strongest male, but she benefits a hell of a lot of the male stays with her instead of just going on to the next female. So she needs a way to show she is better, hence boobs. This is unlike most other mammals where the benefit of the male staying around isn't that strong, so the females will often instead focus mostly on traits for surviving the environment, and the males are the once who have exaggerated features.