Look at these cyclists, on ice and not one of them is wearing a helmet and none of them crack their heads open and die.
I posted this more in jest than an actual representation of not needing helmets.
Recently the Womens Institute has been looking into backing mandatory helmet laws. As adults who have cycling experience, you are unlikely to fall of your bicycle by your self. You are more likely to be knocked off your bicycle by a hard moving vehicle. A collision which involves forces outside of the design parameters of a bicycle helmet.
Just look at the other countries which have mandatory helmet laws, cycling levels have dropped but a considerable amount.
It would be better to target the cause of bicycle accidents rather than try to force people to use protection which doesn’t actually protect you in all circumstances.