I think the sheer number of times we've had people step in talking about how helmets save lives, and the general prevailing attitude that you must pop on a helmet before riding in the same manner you must buckle up, is general evidence that people over-estimate their capabilities. If you don't wear a helmet, it becomes evident soon from all the misinformed folks who start harping on you that they think it does something that it doesn't do. I can't think of a single person in my circle that I didn't have to explain my reasoning to; they were all convinced that "helmet's just work". I was one of them.

Do you contend society is actually well-informed about the efficacy of helmets?