A self-rescue scenario on the other hand is a different matter. You might get knocked unconscious or hurt pretty badly. People react differently to that sort of thing so it's good knowing (through training or previous experience) how you react under real stress.
This discussion so far seems to assume that getting out of the seat belt and the vehicle is the first priority and a good thing. This is not true if you "are hurt pretty badly." Hasty evacuation before stabilization of injuries, especially those to the spinal column, can turn routine trauma into a much worse situation.