Our experiences are similar. Parents can prop kids up to give the appearance of success among their peers. But until the supports are gone and they have to start assuming their own responsibilities—with no one else to fall back upon—they aren’t fully fledged men and women. Their parents do them a disservice if they can’t build in them the confidence to strike out on their own.
Of course, "kicking them to the curb" is an exaggeration but that is how it feels to many parents. As a result, the kids never leave and that does both a disservice to the kids (who never grow up) and to the parents (who should at that stage in their life be downsizing and saving for retirement).