The problem is this patriarchal idea that men should be the main breadwinner. Our culture tells them they've failed at being men if they're not the main breadwinner. It also tells them they need to go all-out making money, which makes it easier for employers to convince them to make long hours. At the same time, women have this cultural role of mothers, where they should be concerned with having children, and put their children before their job, and therefore can't be expected to work as hard as men.
Alright, that doesn't explain why women are more prominent in other hard-working jobs like medicine and law. Still, it's a cultural prejudice that's still very much felt in much of society.
So there have been studies about this phenomenon (women not wanting to marry down), but I am too lazy to Google for them.
Also, financial troubles of the husband are the strongest indicator for impeding divorce. And breakups are usually initiated by women.
Every time this comes up I wonder if I should launch a dating site for rich women seeking a "houseman" for a partner. But somehow I am still not convinced yet that there is really such a huge market.
And, as always: on average...
If you don't see it, I don't think I can convince you. There is much to learn about how the world turns.
In a healthy relationship, this is stuff you work out together, not through demands and womb-based bargaining chips.