Biological drive. But the feminists did push career and “accomplishments”, such that a third of college educated European women have no children while it is 20% of Americans. In prior generations, 10% were childless, so there are 2-3 times as many women not having kids because they were told they shouldn’t.
The wave of articles on egg freezing and 40 year olds having fertility treatment and the growth of first time moms over 35 are proof many women have waited until the clock almost ran out and are now rushing to get one in before they can’t have a kid. So that says many women want at least one biological child but put career first until realizing, no, you can’t just have 2 at 40.
For those who are younger having kids, it is a balancing of family impulse with financial pressures - you want kids, but you have been told you have to have a job so you can support yourself if he leaves or loses his job. For others, you work when they are young so you don’t face as sharp an income drop returning to the workforce after having kids, so you can afford to save for college and retirement.
I have no sympathy for people (both men & women) who deferred having children past early 30s for financial reasons; it is simply impractical and risky.
In my area towns that are 75% Anglo are 75% non-Anglo in the under-20 demographic; the anti-school tax campaign here in NJ, originally fueled by taxes alone, and now compounded as American taxpayers realize they are paying for schools with few American students.