What stats are you referring to? The Netherlands has one of the lowest per-km cyclist fatality rates in the world, at least with 2009 numbers[1]. Would be interested to see if that has changed.
(Some extra nuance: it is of course true that, ceteris paribus, wearing helmets is strictly safer. It's just that the Dutch stats show that proper infrastructure is even more important, and cyclists are less of a danger to other traffic participants than people in cars, which is why there's no stronger push for making people wear helmets — it might cause them to stop cycling. At an individual level, for sure, wear helmets, but as a society, there are better things to focus on when it comes to traffic safety.)
I don't actually know how strong the evidence is for that.
I don't actually know how strong the evidence is for that.