I am guessing it's because motorcycles are capable of going faster, accelerating quicker, so people go faster on them and tend to drive more aggressively. I'd s

I am guessing it's because motorcycles are capable of going faster, accelerating quicker, so people go faster on them and tend to drive more aggressively. I'd say, at the same speeds, a motorcyclist is much more likely to be injured than a driver. In one case, the car is the crumple zone, in the other the motorcyclist's body is the crumple zone.