In fact, there are, on average, more people who tend to behave in risky ways among motorcycle riders than among general population. That's why some of them get a motorcycle in the first place. This is confirmed by the fact that when car and motorcycle crashes are examined, the motorcycle operator is statistically more likely to have alcohol in his blood at the time of the crash.

This is not to label all motorcycle riders scruffy outlaws with no regards for safety. Most of them aren't, I'm sure. But there are more of them among motorcyclists than among the general public.