Because it's the worst kind of ad hoc evolutionary psych bs?
Women marry a lot of different kinds of men, for example: men who make them laugh. Men who are attentive, or ambitious, or well spoken, travelled, groomed, serious, sensitive, quiet, gregarious or any number of adjectives, none of which directly reflect their income.
In simple terms, a lot of,the thread here is guys super imposing the logic of power and position onto 'women'.
A specific type of person seeks mates primarily because of their position, these tend to be ambitious and ambition valuing people.
This is in no way the full set of women.
Yes Statistically, the logic of evolution will result in a bias. Women would love to marry an Adonis who was a PE fund owner, or a cardio-neuron surgeon.
It doesn't mean people wither away, waiting for it to happen.
The most popular trope is not of dr rich, or mr moneybags - its Prince Charming.
Your spouse will be found through the places you visit, the education you attend, via the people you meet, the places you work and and the hobbies you enjoy.
Not just because of the size of your paycheck.
And your spouse will very likely try their level best (all things held equal) to help you out when your paycheck is down, the same way many wives have been all through the recession when people were laid off, and their husbands (and themselves) weren't rising up the corporate ladder.
You may never know why, precisely, your spouse decided you were worth spending the rest of their life with.
But its not just because of biological programming.