Actually, it's really striking that even in America -- the developed country with the #1 highest birthrate -- still falls below the replacement rate. What is it that's inversely correlated between growing wealth and having children? Especially since it was likely to opposite for most of human history? (i.e. large families were a sign of wealth and power).
PS - I can't resist offering my own experience as a parent - what a treasure to have discovered that I'm capable of such love, and to get to watch this love transform me into a better person than who I was before. This kind of love demands everything of you, but through it you discover a truer and stronger version of yourself too.
None of this is conducive to starting a family.
Having all the stuff that could happen during the day if it were (if you will) someone's full-time job, instead get crammed into evenings and weekends when you're trying to also do non-chore stuff with your kids (or, for god's sake, maybe get just one measly hour to do something you want to do, alone... or spend time with your spouse, without kids...) and take care of things that have to happen each evening (dinner, bed time stuff) really, really sucks.
Not having chores piling up through the week to ambush you both on the weekend would be amazing. I can hardly even imagine how much more free we'd feel. With two working parents it's like neither ever gets any actual time off that they're not carving out by neglecting something they really ought to be doing (usually several somethings)
But as you say, I suppose everyone ends up becoming strong. Because there is no other way...
I think a lot of people miss the simple fact that some people just don't want kids and are unable to reconcile their personal experience with anyone else's.
My partner and I are both wealthy enough that we could both afford children and we can afford to not have children. But neither of us think our lives would be improved by having them.
I think that's really, really hard to understand for a lot of parents and people who want to be parents: being (relatively) wealthy creates choice, and that a growing number of people are choosing different things now that they have the ability to do so.
It's fairly obvious the world will be very different and much less pleasant place by 2050. A lot of people don't want their kids to live through that.
It's possible aliens will arrive before then and fix all our problems, or some other Salvatio Ex Machina, but it's not exactly a high-odds bet.
This bullshit excuse that somebody can't afford to have kids is proven wrong by the fact that poorer people have more kids than rich people. You can even be unemployed. Gone are the days of destitute single mothers having to give up their child to the church and work in the poorhouse. We have social welfare for that.
Maybe the fact that poor people can have lots of kids has taken away their value as a status symbol for wealth?
In the past both poor and rich tended to have tons of kids, this is because kids tended to die young regardless of being rich or poor.
Then you're trying to compare massive social changes in the west that occurred around the same time. For example womens suffrage, women being allowed to work, sexual revolutions and birth control.
If you look at countries that tended to develop later, the rate of childbirth tends to drop with accessibility to birth control and education.
There's a well known aphorism about this...