One of the classic studies from Evolutionary Psychology, one that gets mentioned in all the textbooks and is known to all students of the field, perfectly illustrates a line from the Rosanne Cash song Seven Year Ache: Heartaches are heroes when their pockets are full.
It's best known as the "Burger King study." The researcher, John Marshall Townsend, an anthropology professor at Syracuse University, dressed the same man in two different ways. One was a Burger King uniform, and the other was a white shirt with nice tie and watch and a navy blazer. He had women look a photo of the man and evaluate to what extent they would: like to have coffee with him, date him, have 'uncommitted sex' with him (a favorite question of EP), have a serious involvement with him, have a serious sexual relationship, and marry him (another favorite EP question). Unsurprisingly, women across the board rated the nicely dressed man higher.
Perhaps a better song and line to pair with it is ZZ Top's Sharp Dressed Man: Every girl's crazy 'bout a sharp-dressed man.
The real question then becomes why? Why do women prefer a sharp-dressed man. Ah, sure, women want a good provider. But why? The answer depends on who you ask. Ask an evolutionary psychologist and they'll tell you it's because ancestral women who chose men to mate with who showed signs of status and wealth left more offspring than women who were indifferent to wealth. Ask a member of the "Flat Earth Society," what some evolutionary psychologists call women's studies departments, and they'll say it's because women learn to prefer wealthy men because that's what our culture values. I say it's what our culture values for a good reason: Those values helped us thrive as a species.
The need for women to prefer wealthy men has a lot, I think, to do with the ecological conditions women have customarily faced, namely, lower status. Another significant one is having babies that are metabolically costly and also incredibly difficult to care for, compared to other species. Human babies are basically born before they should be. They come out of the womb much less developed and far more dependent on mom than other primate babies, including other great apes, who also have very dependent babies. Human babies require significantly more care and that is made a lot easier with the help of another parent who can provide food, shelter and protection. The higher status the helper, the better fed the baby and the more likely to survive. That's how the theory goes.
There are some feminist evolutionary psychologists who doubt whether that helper actually was a male sexual partner. The other helper (or helpers most likely) could have been a mother, grandmother or other females raising babies cooperatively.