You are: 1. Consuming medical and emergency resources by creating easily preventable severe injuries 2. Raising raising insurance premiums or burdening public hospitals with the same 3. Potentially burdening the legal system (with a higher likelihood of insurance disputes and because more severe injuries are correlated with a higher probability of a lawsuit against other driver) 4. Endangering your passengers (possibly your children) by making it likely you will be unconscious or less able to get them to safety after a collision and teaching them habits that will make them more likely to die in an accident over the course of their lifetime So, yes, it's completely reasonable for society to impose almost zero cost on you to fasten a seatbelt in exchange for avoiding potentially huge externalities.

Wearing a seatbelt might free up a hospital bed for someone else.

You should also be allowed to do that.