Earlier quoted context omitted.
I wonder if salaries were more competitive because there were less workers? If the cultural norm was to only have one parent work, then it seems like the supply of workers essentially doubles* if both parents work, leading to less competitive wages. *not exactly, but essentially. Yes, not everyone is married etc.
The salaries were not more competitive than they are now. Families who raised children on one income back then quite simply expected and did with much less than single income families do today, not to mention with how much two income families make today.
It seems like both parents work to pay for child costs that exist because both parents work.