It's difficult to word the question to suit everyone. I think that, "regularly wear" is the best way to determine who is a helmet wearer and who is not. Isn't this what we are trying to determine? If the question had said, "always wear" I think that the poll would have shown that hardly anyone wears a helmet. I class myself as a wearer of a cycling helmet, but if the question had asked if I always wear one, then I would have to have answered no because there have been occasions when I have not for a multitude of reasons, including forgetting to put it on. To ask if I regularly wear a helmet gets closer to the truth and best reflects my position on the subject. I suspect that this is the case for the vast majority too.
I've never joined in on the helmet debate, but I don't understand why people don't wear them. Even if they offer a small amount of protection, doesn't it make sense to take up that additional protection.
Accidents and their consequences are rarely just that. They are the result of a series of circumstances, coming together, some of which you can control and others which are completely out of your control. The trick is to reduce the probability of all the circumstances conspiring against you. That is all that you can do. A cycle helmet can only lower the probability, so why not take it up? I don't buy into all the rubbish concerning attitudes changing when wearing / not wearing a helmet, it's the work of people who wear potatoes on their feet instead of shoes.
Accidents can be likened to Swiss cheese. In some instances, all the holes line up and you can see through the cheese, similarly all the circumstances can line up to cause an,"accident." In my opinion, a cycle helmet plugs one of the holes in the cheese.
You can't say, I won't have an accident because I've not had one for X years, therefore I am doing everything correctly and will continue in the same way for ever. It's possible that you have been acting in a very dangerous way for X years and simply got away with it. The holes in the cheese just never lined up. You need to be constantly plugging the holes with whatever you can.