It's a perspective that often gets lost in the macro-level fertility discussions: how many births never happen not because people don’t want kids, but because the only off-ramp they might've taken got paved over by modern expectations, norms and etc
In the present, how many of your daily actions and decisions are made not because you want to but because of social expectations or norms?
Is there any utility to having social expectations or norms that push you to do things that you may not “want” to?
In the past, people had kids because that's just what happened between people. Pregnancy was a natural consequence of human life.
Making childbearing a choice means that you need some social framework to encourage it, otherwise it becomes completely gauche and impractical. In the absence of this supportive social framework, fertility rates will drop, and in many cases precipitously. The long-term consequence of that drop in fertility is, at its most extreme, the collapse of modern civilization.
Compare Israel with South Korea, for example. Both are mostly developed economies. In one of these societies, kids are a status symbol; in the other, they are generally considered a nuisance (e.g. kids will often be banned from restaurants or other social watering holes). Can you guess which one of these societies will survive longer?
