+1. A young friend of mine who was a wrench at a local shop got hit at slow speed when a car pulled out in front of her. She hit her head on the ground. She was not wearing a helmet, suffered a closed head injury as a result and was in a coma for a while. I went to see her in the hospital after she came out of the coma but still had the breathing tube in. It was most disturbing. I almost became ill and needed a stiff drink afterwards. And I have known plenty of other people (including myself) who have hit their heads hard in falls that have had nothing to do with cars or dirt roads.

I guess a helmet is like a life jacket. You don't need it until you need it, and when you do need it and don't have it on, it might be too late.