Part of the reason is that because bike usage is so common and the infrastructure is very separate (bike lanes everywhere, no mixed traffic on eg roundabouts), and bikes almost always have right of way and are not to blame in an accident, that drivers are very aware of them. I noticed in countries like Ireland with much less bikes that bike lanes sometimes just end in the middle of a high speed roundabout. And most drivers there have no clue which is in part because until 10 years ago you could just buy a driver's license at the post office. It was a "learner's permit" but it was normal practice to just go and drive.

So yeah in Ireland I wouldn't even ride a bike with a helmet. In Holland I'm much safer even without one.