It's a modern-day translation, or simplification, of the biological imperative.

We are, generally speaking, driven to reproduce and support children.

If you translate money as 'means to support children' then what you have is the idea that a man with money would seek to woo more women, so he could have more children and support all of them (or at least convince women he would support them for long enough to have them) while a woman (who already had children) would be content to support her children without having to deal with a man.

"Women are golddiggers" is a slur translation of this - women, consciously or unconsciously, look for men who can be good providers. For some women that translates to strong men who can fend off attacks and for others it means rich men who can easily afford to care for a family.

"Men just want sex" because that is how they make children. Men are more interested in reproduction than nurturing.

These are all just tropes. No person is ever bound by them, obviously. Everyone is as free to be as much of an exception as they like (as all of the top comments are intent on demonstrating). However, it is foolish to deny that we are animals, that we arose under the same evolutionary paradigm as all of the other animals. There are kernels of evolutionary truth in these generalizations that our culture can cover up, but not entirely remove.