There's another reason to think seat belt laws have been counterproductive. Before government made seat belts mandatory, several automakers offered them as options. Volvo ran ads touting seat belts, laminated glass, padded dashboards, etc., as the sort of things that responsible parents should want. I concede that government action expanded seat belt use faster than would have otherwise happened, but by interfering with the market, government also stifled innovation. That kills people.
Here's my reasoning: The first government mandate created a standard for seat belts. That relieved auto companies of the need to compete on seat belt safety and comfort. Drivers and passengers haven't benefitted from improvements competitive carmakers might have made.
If every auto company were trying to invent a better belt, today, instead of one seat belt, I bet there'd be six, and all would be better and more comfortable than today's standard. Because they would be more comfortable, more passengers would wear them. Over time, the free market in seat belts would save more lives.
We don't know what good things we might have if the heavy foot of government didn't step in to limit our options.
In a free country, it should be up to adult individuals to make their own choices about risk. Patrick Henry didn't say, "Give me safety, or give me death." Liberty is what America is supposed to be about.
Let's start treating people as though their bodies belong to them, not to a controlling and "protective" government.