Well, it's really pretty simple. Countries like Japan are already seeing it. In the next fifty years Japan will have more elderly and retired citizens than any other group. The economy regards retired individuals as a burden, and as a result so do we as individuals, because capitalism. ¯\_(ツ)_/¯
Their economy and currency is also likely first to collapse of the first world nations. Coincidence? The conditions that most make your government desperate for you to crank out kids also most make people scared to have kids.
It's a machine we didn't develop that we're forced to either live with or let die.