I know for me personally, it's not economic reasons as to why I have not had children, but more a problem of finding the right mate at the right time. Some people just aren't socially fit for each other...
She ended up with two. Pregnancy sounds nice and well until your teeth start falling out. Some women just have a really rough time of it - so doing it while also being the primary caregiver for 1 or more other young child... yeah, even if you're financially stable and supported from your spouse's job, that is really a hard thing to manage.
In her case, it seems extra hard because neither her parents nor her husband's have helped with caring for the kids.
Meanwhile, my step-sister (who is less financially well-off than my friend) has 3, but they are constantly hanging out at my parents place or with extended family. Having nearby family that wants to help makes such a huge difference.
I'll add religion to the mix. We're less religious now. Even folks who are religious now(at least in the Christian West) seem to practice a different religion than we did 50 years ago. Religion does many things, good and bad, but it definitely prizes children and reproduction. If it didn't, it would quickly get replaced by a mode of thought/belief which did. I'm not advocating for religion here, just stating that it likely plays a large role in reproduction.