My idea is that much like Psychologists get interested in Psychology because of some disorder of their own that they want to fix, Philosophers don't really understand the point of life, they can't 'deal' well with people and they need to understand some deeper order to the universe that makes sense to them in order to live 'normal' lives.
I will agree to the vast generalization, but specifics wreck the argument.
That sounded kinda retarded, but I'll leave it.
Its like saying doctors want to cure illness because they are sick, or carpenters want to build nice houses because their own houses are shambles.
I've had some experience with Psychiatrists and their kind. They are doctors. Psychologists are not. Whatever, its a good profession, and the ones that are good are really good. Thats the way the cookie crumbles in the medical profession.
Why they do it? Thats a case by case scenario. Some are just assholes who enjoy fat paychecks. Some are wonderful people who want to help people and are trained properly, they spend their whole life seeking knowledge and applying it to problems. I wont badmouth the profession, just the ones who suck at it.
Philosophers are a little different. Its difficult to determine the good that can come out of the philosophers work. Maybe its a noble cause to dissect the reasons people do what they do, but most of them dont matter. All they can do is teach the next breed to think in their own fashion if they themselves are not spectacular participants in the philosophy game.
Peters Principle applies to the philosophy game. People rise to the level of their incompetence. They can go no further. I think when they reach that point, they owe it to the student to admit their flaws but most scholars wont ever do that.