
I could probably be convinced that buckling a seatbelt shouldn’t be legally enforced unless it involves children, but I do think that subsidies which incentivize car companies to make their shit beep really loudly when seatbelts are unbuckled, or taxes that relate to a lack of safety are both great.
Social pressure alters agency, cars are not solo vehicles. Three people in a car choosing not to wear a seatbelt could greatly impact the behavior of the fourth passenger, the reduction of agency towards a life altering or ending outcome outweighs any amount of agency towards minor inconvenience.