Seatbelt sure save lives, probably saved mine, or at least prevented serious injury, over 4 years ago when I girl in a Civic spun out 180 degrees in front of me on black ice. I hit her head on, it was a 4 lane highway with no divider and when the cop arrived he thought that we were going the opposite directions and one of us crossed the yellow line. It took me like 10 minutes to explain exactly what happened so that his report would be accurate. To this day I have no clue how she managed that, as the road was straight.
The girl was shaken up pretty bad, but she was OK and no ambulance was needed. I always make sure the seatbelt is tight around my clothes and seat further from the steering wheel, so I never even hit the airbag and came out without a scratch.