I was focusing on the false equivalence between casualties from vehicles and those from contrived scenarios. Vehicles are a leading cause of death. If you start from empirical reality instead of the abstract concept of “danger” then it is not a mystery why there are seatbelt laws but no goomba stomp laws.
Having acknowledged the shift from that to this new consideration, the question of whether many casualties could have been prevented by seatbelt use. The answer is yes. Many casualties would have been prevented by use of a seatbelt.
Traffic today is denser and faster than even at the time seatbelt laws were introduced. High-performance cars are very accessible today. Road speeds are higher — you can’t drive as fast in some rickety steel Cadillac from the 70s as you can in a Tesla. Brakes and tires have also improved significantly, so people have more confidence driving fast.