a) they don’t want to pay the salary required for there to be SAHMs. That is, single-income head-of-household married earners are the exception and have been for decades.
b, c, d, e etc, all grow from that. All of it. If you’ve ever seen middle class or below American families ATTEMPT a single earning with SAHM, it fails unless drastic austerity measures are taken by the family. This is by design so they do not have to pay the salaries they did during the 1950s when the us government was supplementing the incomes of large corporations post-war to help support the mortgage indus… well you know the rest.