It's, by and large, because those are not the men that women select to have children with. When women consistently choose the man with the six figure salary, but that implies working long hours, what follows is predictable.
There is also a high degree of adverse selection there because a woman can't tell how much a man will help with the children before she has the children, by which point the father is already chosen. So they choose based on what they do know (e.g. salary) which is inversely correlated with that.
If we look at top 50% highest earners among men and compare with the bottom 50%, who has:
Highest Social status. Has more children. Bigger social support system. Live longer. Better health. Feeling of happiness and fulfillment.
For comparison do the same with women and take the top and bottom 50% and collect the same data.
From this simple data driven study we can prove if there exist an incentive in the form of pure outcomes between focusing on activities that raise income compared to activities of social value but without any monetary rewards. We also get a gendered perspective on the question.