I don’t believe this is a “natural female instinct.”

This merely arises due to incentives caused by patriarchal society.

If you’re a beautiful girl in her early 20s, do you focus on building your career or do you focus on marrying a rich guy? Assuming you know you are not as likely to be as successful as he is, even if you’re just as capable? Also assume you know that men mainly value you for your looks. Your ability to provide will not add much to your prospective mate value. And the reason these values exist is because of patriarchy.