girls like rich men because it's in our genes.

in the animal kingdom, some male animals will build nests as part of a courting ritual. The female will then choose her potential mate based on the size of their nest. The bigger the nest the higher the chance to be selected. An example of the top of my head is the dung beetle xD Go google it!

In the human world, the size of the nest translates to amount of money. Everything is so material today. Which girl wouldn't want an awesome nest (mansion) to raise her family in. It would ensure her children's future too (university, health, food etc)

It is part of nature