But they do have agency. For example, if you don’t like the deal being offered where you have kids and then work to the bone to skirt by so that someone else’s line goes up, you can choose to not have kids.
Eventually, this will impact the other person who wants their line goes up.
And from my mid 30s cohort and younger acquaintences, I think that while they do not explicitly say their decision is about someone else’s line going up, the implication is there that if they cannot afford their kids a certain minimum quality of life, then they are willing to go without kids.
More specifically, if they are going to have to deal with living in a cramped apartment (in their preferred location) and the volatility of rents or a giant mortgage, then they are willing to forego having kids.