The men in question worked hard because they really wanted to have families of their own
Why would I rather work for money (hereafter “work”) 2n hours a week and marry someone who doesn't work at all than work n hours a week and marry someone who works n hours a week (assuming the former is what you mean by “have families of their own”)? I don't get it.
Economies of scale come into play here too. If you can get to the point where 2n is a typical job, then having two part-time jobs is likely to not offer as many benefits or long term opportunities as a single full time job. Even if n is a full time job, depending on the job, having one person work massive amounts of hours is probably better for long term promotion potential than two people putting in the bare minimum and constantly having to take time off to take care of children.
Also, as others have noted, a stay-at-home parent is not someone who "...
Dalrock writes an interesting article related to Dr. Helen Smith's book the Marriage Strike. I really have to bump it up on my too rapidly growing reading list. (^_^)