Been kind of nice. Normally, I get only nominal responses to serious, non-personal entries. My last two entries asking about how much a life is worth and what the reasoning behind requiring airbags really is have generated interesting and serious responses.
My answer on the second question of why the government requires it if people don't buy it essentially comes down to the same answer posted in a couple of comments: cost. Door locks are cheap. The benefit is primarily attributable to the owner of the vehicle. The cost of air bags are expensive. The benefit to an individual is actually pretty remote. So why pay for something expensive when I can just drive better. But the actual cost in lives and medical bills falls a lot more on non-owners. Government often has to pick up the tab because many people aren't equipped to cover the costs of catastrophic injury.
Still, the cost to consumers is high. Cost Per Life Saved By The Federal Motor Vehical Safety Standards is a government report on the costs of things such as air bags and seat belts. Unfortunately, it doesn't break out the cost to individual items like air bags vs. seat belts. However, it does say that in 2002, the standards cost $544,482 per life saved. That tab is averaged out to everyone. However, it doesn't take into account reduced injuries, just lives saved. So is that cost worth it to you? Obviously it will be if your life is the one saved.
There are a couple of side effects though. A couple of studies have shown that with increased safety devices, people drive more recklessly. Another is that because the cost is bundled with a car and required, there is less incentive for automobile manufacturers to find ways to reduce the cost of air bag systems. If people buy them separately, they'll look at the benefit to themselves and generally only buy them if they think the cost is worth it. So the price of air bags will not drop as fast as it might separately.
Overall, I think a half million dollars is worth it, even if I'm not one who has needed it.