Helmets aren't really the problem in the NHL. It's the speed of the game and the size of the players more than anything else. I think hockey can go a long way toward reducing head injuries by making all the protective gear OTHER THAN helmets thinner and lighter -- and by forcing wooden sticks back into the game.
Forcing the players to wear the helmets and face masks etc allowed the sticks to come up.
The law of unintended consequences writ large here. Because the players had less to worry about wearing the protective gear, the game itself became more dangerous. Players no longer worried about the types of injuries the protective gear mitigated against, so the players got more careless about possible injuries caused by their actions.
And yes, it *WAS* the nannies that forced the issue. The same scolds that try to suppress every type of FUN out there.