Helmets are still the best way to reduce a lot of head injuries among motorists. Cars travel at a much higher speed than pedestrians/bicycles, so it takes a lot

Helmets are still the best way to reduce a lot of head injuries among motorists. Cars travel at a much higher speed than pedestrians/bicycles, so it takes a lot more to dampen the injuries, and auto-related head injuries are simply more common than bicycle-related ones. It's absolutely as reasonable to exhort motorists and pedestrians to wear helmets as it is to exhort cyclists to do so.