I often feel that many instructors are in teaching for all the wrong reasons. Mainly that there are factors preventing them from doing that particular job themselves, and therefore go into teaching because it provides them a paycheck and keeps them connected to their careers without them actually having to do heavy lifting, or shift work, or whatever.
As they often discover, teaching is not an easy occupation, and they struggle with class discipline, motivation, and connecting with their students. Their desire to be in front of students is lacking and that is in turn picked up by those sitting in front of them, and it becomes a terrible circle between instructor and students of no motivation and no desire to make a classroom work. Education goes beyond the information contained in the books that we ask our students to read, and success in school goes beyond scores on a test.