Why Are People Happy With Only Knowing a Little?

It appears that the more knowledgeable you become in a given task the worse you rate your own performance. On the other hand the less you study about a particular task it seems the more you over estimate your abilities at that particular task. Is this why we have so many people the suck at their jobs and the tasks they engage in on a daily basis? How can we as a society, get these people to learn more so they can realize how bad they are at these tasks?