Do you know why it is that you feel strongly about (what I presume to be) the importance of helmet use?

Could it be because of stories you have heard or read about, or the impression of that broken helmet? If so, a clear understanding needs much more than an impression from a story.

It is true that as humans evolved they developed knowledge based on stories, but the modern world has many more complicating factors that were never present during the development of how humans learned via stories, and these factors sometimes works against instinct. In fact, anecdotal stories and emotional connection to a single event is possibly the worst sort of "evidence" and can work against a true understanding of a problem.

I'm always surprised when someone points to a broken helmet as evidence it provided protection from a serious injury. I always think of just how fragile a helmet is. It doesn't take much to break one. When I drop an egg on the kitchen floor and it breaks, I don't think of how that egg shell protected what was inside, or that my laminate protected the cement beneath from being damaged, I just think it's normal that the egg broke because it's not as strong as what it met, just like the impacts (e.g. - impacts with cars) that break a helmet. Beyond it's designed limits, it can't provide any additional protection, just like the egg.