There were 6,159,000 car accidents in the United States in 2005, the most recent year for which statistics are available from the National Highway Traffic Safety Administration. Those accidents resulted in 1.9 million injuries and 42,643 deaths.
Failure to properly document the details of an accident can cost time and money or even change the outcome of a legal battle. The stress of an accident may make it hard for people to write down what's necessary, even if they took time in advance to learn what to record. Just finding a pen and paper (and other basic tools) can be a challenge.