How is it fair that childless people will get to live in a society where other, younger people still exist when they are in their old age?
Maybe there should be a way we can cut you, as a childless person, off from any contact from anyone born after you, because, by your logic, someone else paid for and spent thousands of hours raising them. You can live your life completely, 100% child free, free of other people's burdens—free of people entirely. Why should you benefit from living in a society when you are in no way contributing to the continuation of it?
Easy fix: You get only a percentage of your salary during maternity leave. Say 50%. If they want the money, they come back early.Other people earned that money to pay you. How is that fair to those people?