The answer to "why do people not do this already, even when rational and well-educated?" is likely because in most families both parents have to work, and are p

The answer to "why do people not do this already, even when rational and well-educated?" is likely because in most families both parents have to work, and are probably tired at the end of the day. Relationships take work and it's sometimes easy to slip into a routine where you let the relationship just coast (especially once you have young children and any free time you used to have is out the window).