To be fair a helmet may not have saved him, - but not wearing one would definately not have saved him.
Unfortunately you are far more likely to suffer an injury riding a bike than say driving a car , and the protection we wear on a bike is - well nothing, compared to say someone riding a motorbike.
My helmet has saved my bonce from some hard knocks, either on low hanging branches to good old tarmac
there is is this silly argument why don't pedestrians wear them, but your far more likely to bang your head on a bike than walking down the street , (just look at the % of both and injury %) but many people -I see it all the time , regard the two activities as the same.
but at the end of the day - its your bonce, its upto you how much you value it.
most riders rely on the safety device called
"It won't happen to me - because I'm special"
I suppose it comes down to "Do you feel lucky , Punk!"