I was shocked because people _want_ to have children and the same number of children that they did decades ago, its just economic reasons why they aren't (not cultural shifts or beliefs changing, or wanting to "have a bigger career").
Also, the birthrate in the USA (and most Western world) is already below the replacement rate for decades now. [1]
[1] https://www.iheart.com/content/2019-05-15-birth-rate-in-unit...
EDIT: Sorry, I wasn't understanding your point that families can't afford to have as many kids as they could one generation ago. I agree with you.
Many people assume that people have less kids because preferences and lifestyles have changed, leading to headlines like, "Millennials don't want kids" (And maybe in the same vein, "Millennials are killing cars", "Millennials want smaller homes", etc.)