I wonder if other parents waiting till they can offer the kids more creates pressure. Not only on the parents but the kids as well. I frequently couldn't get what I wanted as a kid, but that was the norm and in fact several kids I went to school with were clearly poorer. However, if I look at kids around me today, they have seemingly everything they could want. If I imagined the majority of the kids around me had had as much stuff, fancy vacations, expensive after-school activities etc. and I had what I had in actuality I would have felt much poorer. Just the after-school activities alone would ruin everything. My friends and family's kids now are always out at clubs and classes and that's where they see their friends. This would put poorer kids at a disadvantage.

But it has gotten harder in some important ways, housing costs as a % of median income have risen by multiples since then. Shelter being thing that probably makes people feel the most insecure

Those 'other things' are generally more optional than shelter, so you'll bid up shelter until you get it while sacrificing those other things. Inelastic demand and inelastic supply is a bad combo.

We see affordability and population growth in places that allow housing.

We don't see population growth without immigration anywhere but third world countries any more, and consistently dropping there too as living standards increase.

While I agree it's a bad combo and could be better, there's nothing to support any notion that cheaper housing will be enough to increase fertility rates.