I always wear my seat belt. Being an ex-police officer I have seen the damage caused when occupants don't. There will always be the case of the person who "couldn't get out" because of their seat belt, but those numbers are out-weighed by the lives saved when wearing them.
I have a work colleague however, who has a letter from his doctor saying that he is unable to wear his seat belt because he has extremely sensitive nipples and it rubs them! No kidding!