Raising children requires a substantial commitment of time – they're undoubtedly rewarding for many who choose to have them, but it's completely reasonable why some people would be hesitant or even opposed to the idea.
Sweden is at 1.66 children per woman and Finland is at 1.37.
United States is at 1.64 and Canada is at 1.40.
Housing, healthcare, education, and transportation are all generally unaffordable, and those are precisely the costs most associated with having children. Add in the tradeoff of one partner staying home vs making money but paying it to childcare for several years, and it's much easier to say "maybe next year".
But more affordable child care and more tax brakes for families with kids is a key.
These days having a kid is like going to prison: woman destroys career and burns savings.
[1] https://www.statista.com/statistics/241530/birth-rate-by-fam...
This has been done, often abused, and the neighborhoods don't always remain decent.
How about just a UBI instead?
Want to fix this in the US? Offer stable child-rearing families FREE housing, and I mean in decent neighborhoods. I don't mean a stipend or low-interest loan, I mean FREE including utilities, maintenance and property tax. You will see strollers everywhere within two years.