Just a guess, but perhaps some combination of the following factors:
sh**ttier cars that are less well maintained
more actual miles driven with less driver training
they get robbed, a lot, sometimes robberies go to sh**t
when they do get in an accident or shot, they don't have a direct line to the cops and other emergency services at the ready
I think there is something to the idea that as much as the police are forced into dangerous situations, they're about as well-prepared for danger as a person possibly could be. Compared to cops, taxi drivers are pretty helpless.
