[Aloha]

The automatic belt systems also had the disadvantage of being fiddly, unreliable and complex. While the airbag is not as effective without belts, its much more reliable, and much less complex mechanically than automatic seatbelts.

[ceejayoz]

That's hardly the only piece of tech the car companies have fought. Air bags and shoulder seat belts, among other things. The National Highway Traffic Safety Act of 1966 appears to be pretty universally cited as the turning point from a rapidly increasing rate of automative deaths to a dramatic, sustained drop over the next few decades.