The difference likely there is in the ‘40s you were seeing improvement after the Great Depression and employment during WWII, followed by the postwar boom. Whereas the past two generations have seen precarity increase while living standards falter if not drop compared to their parents’ generation. So they are striving to recreate what they once experienced in their childhood, yet may never return.
Also the entirety of society including their families emphasizing the importance of higher education, good careers, etc. even as the latter is harder to achieve and the former becomes increasingly devalued, yet pricy.
People had kids even in the 30s, too. During tough times, we have to work harder and endure more adversity. Our great grandparents understood this just fine. In western countries, current generations (including my own) are incredibly soft, and expect that because they know boom times existed before, we are simply owed an equally easy time automatically — but in reality, there are often external factors that just don’t allow that to happen.
Contrast China, for example. 1950-1990 was not a 40-year prosperity party like it was in America and Western Europe. Therefore, they are at least twice as willing as we are to grind, and as a result multiplied their economy an astounding amount over the past 35 years. You can see the same thing in many development countries today. They take nothing for granted.
But people are working harder- they’re simply working harder at their jobs.
It should also be noted that the birth rates in China are not increasing, either, despite the end of the One Child Policy. Partly it is also because the younger generation feels immiseration from higher costs of living and fewer opportunities- see the concept of involution.
Finally, during the Great Depression, fertility rates in the U.S. dropped to all-time lows. Not unlike the Great Recession, which has triggered a nonstop decline. We all live in the shadow of 2008.
Also the entirety of society including their families emphasizing the importance of higher education, good careers, etc. even as the latter is harder to achieve and the former becomes increasingly devalued, yet pricy.