Its true, but [politics incoming] it's harder since the nuclear home resulted in the elimination of community, and both parents are forced to work to get by, and it only looks to be getting worse.
Raising kids is great (for many people), but it shouldn't be your entire life. The unfortunate reality is that work and raising kids is the only life many people have access to.
It's also not really the case that parents are "doing it to keep the population up" so the premise is wrong.
But it's funny to imagine it that way