Nah. This sounds plausible, but it flunks an obvious empirical check: families where one earner brings in all the meaningful income and the other earner makes barely enough more to pay for the child care costs their work incurs. I know a bunch of families like this. Surely some parents work because they have to, but it's also obvious that many other parents work because that's what they need to do to lead a fulfilling life.
As someone who has been a caregiver for school-aged kids (mine are adults now): just what is it that you'd expect a stay-at-home parent to do once all the kids are in K-12 school? The kids are gone for most of the day.
I'm not arguing that all families make the decision to become dual-income households. I'm arguing that there are major economic incentives that push people toward dual-income. This allows for your experience and the observation of counter-examples to co-exist with broad social shifts in family-work structure. The reason it appears true is because it is.
You don't have to accept my word for it.
The other possibility is reading what economists have to say[1] about the effects of inflationary pressures on household income structures. Sorry, but I'm going to put more trust in an expert than someone with anecdotal evidence.
As someone who has been a caregiver for school-aged kids (mine are adults now): just what is it that you'd expect a stay-at-home parent to do once all the kids are in K-12 school? The kids are gone for most of the day.