I think the helmets would just be too much of a hassle, making them mainstream would take people off bikes again? It messes with your hair, it's hot in summer, difficult to combine with a hat in winter, you have to put it somewhere when going places, like bars. And make no mistake, here we jump on an off bikes all day, I would really hate to have to wear one on a bike. (I do wear one when mtb-ing btw!)

I'm 40, lived for all of my life in the Netherlands, I hardly saw any accidents, and I never ever saw any accident where a helmet would be of any use. Yeah it's anecdotal, but I feel it's just safe enough. I feel the same about biking as I do about walking. Helmets wouldn't make it safer. But, show me the data to convince me otherwise. Still, lets say it makes things safer, I wonder if the net effect would still be negative because it would drive people into cars, where you don't need a (stupid!) helmet.

I think it's difficult for people from other places to imagine just how little cars you encounter with good bike paths, and how people drive around you when everybody is a "cyclist" (hate the word, it's just normal here) and a driver. For example in a collision, it's always the car's responsibility [0], because pedestrians and people on bikes are considered vulnerable, they always get 50-100% off their damages paid. It creates a certain culture.

[0] https://www.anwb.nl/juridisch-advies/aanrijding-en-dan/aansp...