How are those analogous? People can live perfectly fine without a child but can't without a job (unless they live at home with their parents which coincidentally a lot of hikikomori do).
The ability to attract and successfully integrate hundreds of thousands of immigrants per year to support an oversized elderly population is not a luxury that most countries that can afford.
For most communities, normalizing childless will only come back to bite people in some form or another.
That's not to say that everyone has the same expectations.