Minimus - They are mentally lazy and do not want to pursue challenging their brains.
I don't believe that assessment is a fair one, at least for most. Children instinctively trust what their parents teach them, even if they tend not to like it. Most of us here did not leave until well into adulthood. Unless we were all mentally lazy, that assessment is just oversimplified, and ultimately, wrong.
Cantleave's point is also a valid one. Human beings are social creatures, and if kids manage to stay past adolescence, the social environment provided tends to reinforce their decision to stay. At that point, it usually takes a life changing event to wake someone up.