I really don't think it's as binary as people make out on here. People are just faced with different choices. Unless you've been in someone else's marriage, circumstances or financial set-up, you can't say what you would have done yourself. It's rarely as binary as SAHM = 'disengaged husband.' It totally depends!
Sometimes, if one partner in a marriage has certain opportunities it makes sense to go for that for a given time. For instance, there is a couple we've known since uni. They got married quite young (about 25). She has not worked since she was about 28 when they had their first DC. He founded a company and would work abroad one week, home the next. They moved out of London to a very rural location so work options for her would have been limited, even if she'd wanted to work. So, some might call him a 'disengaged parent' because he worked away a lot and had a SAHW. If you met him though, he's the most lovely down-to-earn guy and has a brilliant relationship with his kids.The payback for his work focus and her making this easy for him, is that when he was about 40 he made a life-changing amount of money - I'm not sure how much exactly, but about £200 million I think. So since 40, he hasn't really had to work. They still live in the same house as they always lived in and have a very simple life really. But my point is, they had certain opportunities and knew what they were doing as a family. They did it together with the common aim to change their children's futures. Now they are about 50. Not only do they not need to work, but their kids are more than set up for life.
Ok, this is maybe an extreme example, but obviously, there are people out there who have opportunities to make life-changing amounts of money and it's very apparent if you know or are married to someone like this, that they don't generally achieve that by working 9-5 and keeping a tally on who does the laundry! This kind of conversation doesn't even come into it. You may have an average / well paid job, but this may seem irrelevant in the overall financial context. It's no coincidence, that many men around here who have SAHWs also work flexibly or retire quite early eg. in their 40s. By this time, it's not about salaries. The family have made investments and this kind of thing. Ok, it's not 9-5 or 'routine' parenting, but it's not 'detached' either. The kids see and understand what the parents are doing for them and why.