One side doesn't want to admit that a lot of poor people have a good bit of free time available to them, particularly those who receive social services.
The other side doesn't want to admit that middle class and up folks have been working long hours at a cost to their personal lives and development, that isn't new, but now both mom and dad are doing it and households aren't really any better off.
This results in poor people with the time to make and raise children, doing so and receiving government subsidies to provide for them. The problem is the government can't give you time or your youth back so the well off just stopped having kids.