Your logic is flawed.
Not only do seat belts reduce the risk of fatality by 45%, they also reduce the risk of serious injury by 50%.
So it's more like, either end up with a broken collarbone and some bruises, maybe a concussion, or without a belt your best case is in a hositpal bed with some tubes, and your worst case is people paste on the road.
You're much more likely to not end up dead or in a hospital bed if you just wear your damn seat belt.