Wow, I never thought so many would not wear a helmet, even some of the time.
I can't imagine it. And it does bother me when I see riders helmet-less. Just like it bothers me when I see people in cars not wearing seat belts. And yes, I think you should wear helmets skiing and horseback riding. Personally, it wouldn't bother me if skydiving was outlawed. I was once in the ER with my DH when they brought someone in who had been a sky diving accident. Enough said.