That, plus the fact that you can be fired in most other professions. Tenure is the other demon in our current public education system.
RE your post #88 -- Well, teachers who have tenure do not get fired. But not every teacher has tenure either because they moved and don't have enough years in a district or they teach in private schools or whatever. Sometimes teachers get let go because of budget cuts if they are not tenured. What I think would be refreshing is to see some useless administrators get canned once in awhile.