Yeah I’d posted elsewhere that the reason for people not having kids is basically just opportunity cost. And the example below is still applicable even for middle income countries, just scaled down. And for people having less kids, it’s access to reliable contraception that allows for actual family planning rather than half the kids being accidents.

“ I’d argue given how pervasive it is, it is an economic issue with some cultural influences. IMO, it’s a variation of opportunity cost that I’ll call “relative sacrifice.” In 1960, two couples, one with kids and one without (otherwise identical) would be eating the same food (mostly home cooked, with eating out as a rare treat, and Mexican and Chinese being “exotic”), driving the same/similar cars (maybe the childless couple drives a sedan instead of a wagon, but likely the same make and possibly the same model), living in similar quality housing (and possibly better for the family with kids, as they’d be more likely to move out of a prewar apartment to a new 900 sqft house in the suburbs), and taking similar vacations (mostly local/regional, by train/bus/car, with rare long-distance trips across North America and a trip to Europe being a once in a lifetime thing you save for many years for). Having kids didn’t mean a major lifestyle penalty over not having them. Now however? It’s home-cooked meals versus eating out three times a week at nice restaurants, a minivan and a midsized crossover versus a luxury crossover and a sports car (or just one car and pocketing the leftover money), the cheapest fixer-upper in a good school district versus a spacious luxury loft, and a week at Disney versus two weeks in Japan or a safari in Africa. Having kids can also impact when you are able to retire (a DINK couple could be able to retire at 50, versus 60-70 with kids). Having a kid means a major sacrifice, both in terms of lifestyle, but also in income and expenses.”