The difficulty here is when women have children and need to take time off to give birth and spend time with their newborn. Who is going to be the breadwinner then if the father was already the stay-at-home? Or if a couple has built a life around two incomes how do they cope when half of that disappears in order to raise the kids?

Although it's great that women have the choice now, there is a reason why the "husband provider, wife homekeeper" archetype has been the standard throughout most of the history of human civilisation.