Human beings make many more calculated decisions than we realize. We assess risk as best we can and act accordingly. This is why seat belt laws haven't had the results policy-makers had hoped. The reason is when you wear a seat belt, you are essentially lessening the cost of an accident. As anybody who has studied economics can tell you...if you decrease the cost of any activity, you'll wind up with more of it.
Nobody gets in their vehicle and consciously thinks, "Since I'm wearing a seat belt I can afford to drive more recklessly", but that's exactly what happens subconsciously. If you don't believe me, think of the example of the guy who owns a Tahoe and a Metro. He won't necessarily think about it, but one vehicle is a lot safer than the other, so he's probably going to take more caution in the Metro.
If you really want to put a stop to fatal traffic accidents, remove all seat belts and require all manufacturers to put a blade on the steering wheel facing the driver. Under those circumstances there would be no accidents.