Yeah, I guess you've got a good point there. Also, the infrastructures to cycle are not as good here as in The Netherlands.
I just think, based on people's comments, that there's some silly stigma associated to the helmets like "they're ugly" or "you look silly with it". I've only started cycling again a few years ago, after a childhood of cycling every day without any safety gear; it was hard at first to make myself comfortable with the idea of wearing a helmet. Some time later it just feels natural and I actually get worried when I see people without helmet.
It seems to be something similar to the seat belt. It took time for people to get used to it and nowadays I still see that problem in some countries (usually with old people in small towns).