Also, helmets just lessen blows. If you have an impact that is enough to kill you dead on the spot without a helmet, it is probably going to kill you dead with the helmet on. Or leave you in a vegetative state, or leave you crippled. Keep that in mind, they help, but it is a very narrow window that they help with.
Disagree. As a road paramedic who has attended numerous traumas, as well as working at multiple race tracks covering motorcycle racing, open wheelers, ALMS, sprint cars, etc -- wear a helmet. It helps more than you think. Your skull bursts like a watermelon when given the chance