From a medical standpoint:

Seat belts have been proven over decades to reduce the mortality rate involved with major auto accidents. In reality, it's not the seat belt that kills people. Your heart is located left center chest ( not dead center ) and can only travel any one direction so far before fatal damage occurs. If someone dies from an accident but there is no obvious trauma chances are the heart moved too far and ripped the Aorta or maybe cervical damage in your neck occurred. This occurs when the body is stopped by the seat belt but the internal organs continue to move in the direction of travel and the same goes for your neck.

Seat belts save lives plain and simple. Don't wanna wear them in a vehicle equipped with them? That's your choice but I won't have sympathy for you if I have to pick your carcass up from I-75 because you assumed you were too good to wear it or you "forgot" to put it on.