You know how motorists sarcastically refer to cyclists over here? "Crunchies", or something like that.
My work trip is 5 km and all the way is bike roads and pedestrian paths. One of the advantages of living in the nordics, I suppose.
I don't even wear a helmet in the summer - I just pedal intentionally slow.
Anecdote: I was with a group of tourists and we were about to rent bikes for a guided tour. We were offered helmets, but only some were taken. Before we even departed, a girl managed to fall of her bike and injur herself. A second offer to use helmets was met with much more acceptance.
Statistically speaking, dutch don't wear helmets and they don't get much injuries. It's as much about how you cycle and what the routes are like than having or not having a helmet.