Yes, because of the outdated assumption that women take virtually all responsibility for childcare, which is damaging not just to women, but to men and children too, combined with the it becoming more difficult for families to manage on a single income.

It is not just an American problem. It is slowly changing, at least here in the UK: I see a lot more dads taking kids around these days. I have still found people were surprised that my daughter lived with me rather than her mother after divorce though.