a. The opportunity cost of having children is higher in rich countries. (E.g. If you are richer, you can say travel more.. but can't easily if you have kids! Also the income hit from having children is also much higher in rich countries)
b. Rich countries generally have higher social expectations for parental involvement. Kids cost more in rich countries because parents actually do more.
Clearly, there is something more important to you.
I simply said it is clear that you have determined that other things in your life are of greater priority for you.
I'm not sure what you mean by "stupidest". It isn't wrong. For me it is a trivially obvious observation, and thus kind of lame, but I'm a disinterested observer. Making the correct observation would be more difficult if I were deeply invested in the situation.
FYI, my 11 kids are supported on a single income, and I'm just an experienced software hacker. I don't even manage people or work overtime. Granted, I don't get to live anywhere near my childhood home of the Bay Area, but such is life. Just as you have done, I made choices according to my priorities, but my priorities are different.
When you spend ten years telling people all the ways kids will ruin their lives, it doesn't really seem surprising that they'd be hesitant to have kids...
I don't think this is the issue. It's much more a cultural thing, statistically richer countries have lower birthrates. But getting married and having kids is no longer accepted as "just what you do". Less people are getting married, that also may play a role.
I'd also imagine it's different in different areas. Might even map to incomes, or political leanings of different zip codes.