It’s comfortable and cheap living at home with no responsibility and most things done for them. Often it’s sons who tend to return post university or they just remain at home.
Depends on how the parents feel about it, otherwise a family discussion might be necessary.
We left school and home fairly early, got jobs, shared flats, lived in bed sits, paid bills, struggled financially, didn’t go out often, scrimped and saved, lived on the cheapest mince and sausages...well that is my experience, oh yes the 60 s were really swinging, not!
I don’t think they will leave home until they are ready. life these days is full of things material and that’s where the money goes.