It's probably due to magnitude of accident. Injury is caused by unplanned deceleration - sudden, smack into a truck, or gradual, sliding down tarmac. How much deceleration you need to do to stop is directly related to the speed you're doing. Unless you're Lance Armstrong you're probably only doing 10-15mph on a bicycle. I don't know anyone who rides a bike that slow! Also, few cyclists wipe themselves out, but a large proportion of bike accidents are rider error, no-one else involved.
I wouldn't argue with women.. they're pretty smart generally!!
