You're baffled people aren't having kids? What bubble do you live in? People straight up can't afford housing much less children. The avg American is completely priced out of owning a home right now. Edit: the replies - y'all are out of touch. Visit an average family in the Midwest with a household income of < $100k/yr that doesn't own a home yet.
I grew up poor and people never "thought" about affording kids, just had them and figured things out along the way.
It seems it's a self-filtering mechanism in the upper classes, that put all kinds stops before having kids (e.g not ready/mature enough yet, not financially stable, etc) and usually end up having one at most.