A big part of the problem is that couples want to live in big houses, eat out, go on expensive vacations - and that takes two incomes.
When I was growing up, the moms stayed home with their kids (at least until they were in school) and the dads worked. Did that mean that we had to live in a 1200 sf house with one bathroom? Yes, and we were perfectly happy.
People who choose to have children must sacrifice, at least in the early years, by living very modestly - as opposed to living a $130,000 HHI lifestyle and then expecting other people to pay for child care.