Just reminded me of this bit by Jerry Seinfeld,

"There are many things that we can point to that proof that the human being is not smart. The helmet is my personal favorite. The fact that we had to invent the helmet. Now why did we invent the helmet? Well, because we were participating in many activities that were cracking our heads. We looked at the situation. We chose not to avoid these activities, but to just make little plastic hats so that we can continue our head-cracking lifestyles.
The only thing dumber than the helmet is the helmet law, the point of which is to protect a brain that is functioning so poorly, it’s not even trying to stop the cracking of the head that it’s in…"

Anyway, just to add my personal story--went mountain biking several years ago. We were on a fireroad hauling. Didn't see a dip, went over, landed right on the top of my head. Cracked the helmet right down the middle. My neck was sore for several days, but nothing other than that. It appeared, from the outer shell of the helmet, that I landed on a rock. Full body weight propelling the head towards a rock wouldn't have been a pretty sight. That helmet saved a lot of pain or even my life. I never go riding without a helmet.

I don't care what the stats say, what people's opinions are, etc. IMO, you can't "predict" what's going to happen in a situation with 1 billion-trillion variables. Maybe you've gotten lucky not hitting your head when you've gone down in the past, but it only takes one time....... then you're paralyzed, scarred, or dead. I don't care if you're on the road, dirt, snow, water, whatever. PROTECT YOUR HEAD!!!