As someone who with some frequency has to deal with the gore and horror of auto crashes where people didn't wear seatbelts, I can testify that it does harm the first responders as well. And uses a fair bit of taxpayer resources - fire/ems, helicopters, regional trauma centers, that sort of thing.
It is also the case that if you are wearing a seatbelt, you can better retain control of your vehicle during vigorous maneuvering, which may allow you a chance to avoid an accident in the first place.
In my state, you can drive without a seatbelt all you want, as long as you don't do it on the public roads...