The true teacher defends his pupils against his own personal influence. He inspires self-distrust. He guides their eyes from himself to the spirit that quickens him. He will have no disciple. -Amos Bronson AlcottI know how important motivation is, and I know exactly how unmotivated N percent of the population is. I'm not arguing against motivation, but that perhaps we shouldn't worry so much about motivating the kids.
First of all, there may not be too much teachers can do about motivating some kids. There are some kids who have perfectly good reasons not to like school -- those who've been savaged by previous classroom experiences; those who have been told in X ways that they're stupid Y times per day for Z years of schooling; and finally, those who correctly see school as irrelevant to their problems. Let's get real: school is not the solution for all of life's inadequacies (and the way many legislatures, administrators, and professors operate, it soon may not be the solution for any of them).
Another reality check: in trying to get and hold little Johnny's attention, no matter how interesting, entertaining, and motivating I am as a teacher, I still will have trouble competing successfully with little Britney's chest. Sometimes, in fact, motivation just boils down to making it more unpleasant for the kid not to learn than it is for the kid to learn. Certainly we must be careful here: this sort of reasoning has been used far too often to excuse cruel teaching practices by lazy incompetents.
To examine this issue further, see Motivation: why is this a worry?