They often didn't have head rests, so whiplash. They also came from a time when shoulder belts weren't common and seat belts in general were more of a suggestion.

And then there were the days when parents would stuff too many kids into the front of a single cab with a bench seat and put us 2 to a seat belt, and / or one kid on the lap of the driver. But those were also the days of the rear facing seat in the station wagon. I also remember my scout leader packing a group of us into the bed of a pickup, shit was scary but so much fun.