Some car manufacturer go for air bags, some for automatic seat belts. People hate automatic seat belt more than the manual ones. Car makers go with the air bags. People still don't wear seat belts. Air bags start killing people.
Government adds rules, regulations, and punishments for air bag use.
Let's follow that logic - If air bags are as good as automatic seatbelts, and manual belts are as good as automatic ones, then air bags must be just as good as manual seatbelts. But people don't wear them. This means the only people to get screwed are the responsible ones who always wore their seatbelt - now they must pay for an expensive, complicated, explosive device which is of little use if you're wearing a seatbelt. But wait, there's more. Now the government must really enforce the seat belt laws, mainly to protect us from the air bags, especially in the more common low speed accidents where the air bag add to injuries, even fatalities.