Back in '67 only dad had to work to support his family. Now I am sure those numbers reflect mom and dad working. Do we really have a richer society when both parents have to work?
Nope.
Then prove it.
We have an incredibly larger number of households now compared to 1967 and even with that increase in numbers, the average real income of the American family has risen dramatically. I suspect, should you really do your homework, that you'd find that the number of single parent households today is very large and refutes your assertion that the increase in income over the years is solely because both parents are working.