This will not change unless housing is fixed.
Not only do parents need to pay for housing, but also for more food, more clothes, child care, sometimes school, and depending on the country extra wear and tear on a car or if it's a multi-child family, a larger vehicle like a minivan. And that's just the financial cost… good parenting also requires more time than can be alotted in modern industrialized society which require one's job to be their life.
It's possible for many to just barely scrape by on their wages with kids in tow, but why would anybody subject themselves to that struggle if they don't have to? If one is serious about having kids it's better to wait until both parents-to-be have achieved higher salaries and saved up significant financial padding to help mitigate disaster. Problem is, many people will never make that kind of money, and thus will never have kids. Others who would find themselves facing fertility issues brought on by age by the time the means is available.
Another way to word this is "the very wealthy increasingly consolidating all wealth to themselves."
It's a fundamentally selfless action to raise children. It is also part of the core purpose of all living creatures.