So, if I get insurance with a company that doesn't cover unseatbelted people and the other guy has the same policy (because it's cheaper) and he doesn't wear his seatbelt and we get in an accident and he's injuried, who pays for it? By youir definition, nobody does.
Except the insurance company or the government.
I think what he means is if you don't wear a seat belt, and you get hurt, then your insurance company does not have to pay for it. If someone hurts you but they don't wear a seat belt and you do, their company still has to pay for your injuries.