Because people in general are idiots.

Or, to express it more charitably - we're all used to it. Car-related fatalities no longer register as unusual. You don't hear much about them in the news. They're treated as "something that unavoidably happens to people". Like cancer or heart attack, and unlike murder, which is unusual. I'm willing to bet that you're friends or acquaintances with people who crashed their cars (with or without health consequences), and you're at most two hops in your social graph from people who died in a car accident.