It's just not healthy past a certain point.
It's become so socially acceptable to stay with your parents well into your thirties and this is not good for anyone's mental health, IMO. It's not fair on the parents either. They spent the first 18 years raising kids, it's only fair they should be allowed the space to themselves again so they can get back to having a life again.
Obviously economics comes into it, and it's a way to save money for a home of your own, which I get...well, not really, I never wanted a mortgage or anything like that, but I can see why people do it. What's the point though if you all end up mentally unwell because of it?
Some people get along with their parents and that's great, but it's still better for your own mental health and sense of independence to get your own place as soon as possible.