Why? What is this is fundamentally what most women want, is to be home with their children when they are young?
oh I'm sorry, I wasn't aware that someone had conducted a poll asking 3.5 billion women what most of them wanted out of life 
Gosh it's lucky that most of them wanted the same thing, and that that thing was a construct that has only really existed since the 20th century, and that that thing allows men to continue with their lives and careers unhampered after reproducing. Huzzah for everyone, problem solved.