Seatbelts should still be voluntary. Just like helmets.
I used to think the same thing, but after designing & building ATDs (crash test dummies) for 4+yrs, seeing the data, and a 3 totalled car crash in person, I'm glad it's enforced. I fully support darwinism, but auto safety has saved many many close people to you in one way or another.
It all started with Colonel Stapp when he realized more of his fighter pilots were being injured/killed in 35mph frontal crashes driving to the base than flying in his aircraft. One of my favorite clips on the advances, and that was 12-13yrs ago: