My wife once called it "affinity porn," in that a lot of demand is the feeling of proximity to something great gives you some kind of essence of that greatness, like it will rub off in some way. Why do people like getting signatures of sports figures (ignoring second order financial motives to serve to the those with genuine interest)? Or to shake the hand of a political or religious leader? So much of the advice literature seems like it falls into that category, especially those that are memoirs in advice-book form.