[bstrand]

It most certainly is a generalized circumstance that Dutch cyclists don't wear helmets. A 1998 study (1) found that 0.1% of them wore a helmet. Furthermore, search for "Amsterdam cyclist" images (2) and you'll find virtually no helmets and rather few of the head coverings you posit are the cause of reduced helmet usage.

1) https://www.aaafoundation.org/sites/default/files/bikeuse_PB... 2) https://www.google.com/search?q=amsterdam+cyclist&espv=2&tbm...