It's possible those kids don't yet exist. Among others, because would-be parents can't afford to work part-time or give up one job to care for the kid.

Is it real estate developer's problem? He builds the building, sells out the apartments and leaves. Where the buyer will put their kids is the buyer's problem.

I agree, I just think there’s some idea that people and cars are magically conjured into existence when homes are built, as though they are currently using no facilities.