The single biggest advancement in automotive safety is the seatbelt, but it is useless until you buckle up. Modern cars will beep at you constantly to let you know to buckle up, but that shouldn’t be the only reason for you to wear a seatbelt.
Every other safety system in a car depends on you wearing your seatbelt to work. Take airbags, for instance, they are usually labeled SRS airbags, which stands for supplementary restraint systems, because they only exist to supplement the seatbelts in the event of a collision. Seatbelts save lives, plain and simple, so use them.