Here's my take: women have kids, then take care of them; while men have kids, and still play in their bands. I've seen it a million times in the visual, writing, and performing arts. Guys keep having their pre-kids life, while women drastically change their lives with the kid's arrival. There are fewer all female bands, fewer female visual artists in galleries, fewer female writers out there reading their stuff because they do more of the kid-raising gig. And as a concert organizer myself, I see it: there are plenty of solo folk guys wandering around, but not too many solo female ones. They drop out of the scene, have a kid, and stay local. I just don't know any guys who give up their livelihoods and avocations when they become dads.