Um, OK, this I gotta see. What kind of statistics can you produce on the number of people killed annually because someone else was ejected from their auto while not wearing a seat belt? I wasn't aware this was a common thing.
I do know of a case years ago where teen-age driver lost control and went flying off into a field. Driver's door opens and driver falls out. He's injured and unconscious but survives. The driverless car then continues on and hits big rock or tree -- I forget which. Passenger is ejected through the windshield, lands in a creek unconscious, and drowns.
That's not an argument for mandatory seatbelts, but it is an argument for anybody with brains to always use seatbelts.
I'm not saying its common. But at 50 km/h, an a person weighing 176 lbs. will strike whatever it hits first with a force of 6,215 lbs. That body is hitting something, maybe in the road. It also is another object that has to be avoided by other drivers.