[wolfgke]

I rather correlate helmet-wearing cyclists to be the "wilder" bikers - since they know that they'll drive dangerously, they better wear a helmet to (feel to?) reduce the most dangerous consequences.

Or to put it in other words: you are more inclined to buy a helmet if you are know that sooner or later you'll surely need its protection. Or since you have a helmet, you know that you can do things at a (psychologically) acceptable risk that you wouldn't do otherwise (the latter phenomenon is called "risk compensation").