I imagine that if you're 77 years old laying down on the street while a car drives over you, wearing a helmet is not going to do a whole lot most of the times.
Its a strange one when looking from the outside (from one of the most cycling happy countries). Here you're considered a feckin muppet if you don't have a bicycle and use it frequently.
(I don't have one though...)
Thought the whole UK drivers vs cyclists thing was a bit of a joke when first...