That's quite true. And they got that via sustained policy to encourage cycling. It's been quite demonstrated that mandatory helmets actively discourage cycling, leading to both a disinvestment in infrastructure and drivers being less comfortable around cyclists (thus more dangerous)

I am not making a point about individual choices. Anyone should feel free to wear a helmet. But public policy is a different beast, and the data on mandatory helmets laws are inconclusive as to benefit and clear as to cost.