Why would they care if they don’t know a life outside of diapers? 

Many parents think their kids should be directing their own lives. They think that their 3-year-old will communicate with them about when they’re ready to be potty trained, but that couldn’t be further from the truth. Kids need their parents to plan their lives and work with them on hitting milestones. Some milestones, like speaking in full sentences, will come naturally to a kid. Learning how to use a toilet is something that needs to be taught by parents. A kid isn’t just going to wake up one day and decide that it’s time for them to be potty-trained. They might be influenced to learn how to do it because they see their older sibling learning how (that’s what happened with my younger sister and me). A kid isn’t going to fully learn how to go to the bathroom if their parent isn’t committed to teaching them and letting them have some accidents along the way. 

Most kids should be potty trained by age 3, but some parents are waiting until their kid is 4 or even 5 before taking pull-ups away. The result is that more and more kids are starting Kindergarten without knowing how to use the restroom, and teachers are at a loss about how to handle this. It’s 2 weeks before Kindergarten starts, and this preschool teacher is miffed that 5 kids in her class are allowed to move on to Kindergarten in Pull-Ups. She’s probably grateful they’re no longer her problem.