I wear one often, but not all the time, and I do like to pootle along with the wind in what's left of my hair…
But then again, I also sometimes rock climb without a helmet, and you know what, sometimes I even do it without a rope!
But then I also do winter climbing, where I do wear a helmet, but the risks involved in that, even with the helmet, probably far outweigh the risks when I am riding without a helmet!
As for people who say they wouldn't help someone who had fallen off and hurt themselves just cos they weren't wearing a helmet… have you really thought about what you are saying?