I've seen couples drift apart pretty quickly once their daily experiences diverge.
If she spends all day working at an office, and he spends all day homemaking and with the kids, then each forgets what the other really does.
"The office" becomes an abstract place that someone just goes and isn't stressful at all. "The home" and "the kids" just magically take care of themselves and don't require much work.
Dual income has its own problems, but it seems a healthier default in terms of reminding people that work is... work.
