Your argument could be made about Health Insurance and dietary, exercise, and lifestyle choices. I expect you would be on the side of mandating exercise, no sugar, only good fats, no anal intercourse - etc. Since all these drive up your health insurance premiums.
Several problems with that statement.
There are still many questions about just which foods are healthy, there can be no question that seat belts save lives.
Also it's a matter of enforcement, you simply cannot enforce rules mandating eating without a true police state, that is not an issue with seat belts.