What does it buy him?

Childbearing years, that is what.

Young women with largish breasts and broad hips have more years of popping out (more likely to be) healthy babies than someone older.

There are evolutionary explanations / 'just so' stories about why
1) Men tend to be attracted to younger women
2) Men tend to be attracted to features such as broad hips and ample brests.

This isn't to condone it... Just to say that one often does see a younger female (child bearing years, nursing an aging male) paired with an older male (good provider for mother and children, social esteem provides some security against illness/loss of income).

A woman who has her own career??? Less likely to be so devoted to his children and him... That is the thought at any rate...