Well you only need the right lottery numbers once. Just a matter of knowing.
Ditto the tortional spinal injuries caused by the helmet induced circumference increase of the head. And MIPS, solving a problem that wouldn't exist if people didn't wear helmets in the first place. The difference there is it's the buying of the helmet in the first place that earns you those six numbers. There is no free lunch.
I'm not anti lid, but it's frightening how many people blithely wear one like some cloak of invincibility when that is far from what you're getting.
On a related aside, far and away the most effective method of improving ones safety odds while riding on or off road is some proper training. It continues to astonish me that people blithely stick a bit of microwave oven packaging on their head in the name of safety while blithely continuing to endanger themselves unnecessarily with their woeful roadcraft. If wearing a helmet is all a rider has done in the name of safety then they haven't really done anything.
And that's the difference between thinking you've done something to make yourself safer, and actually doing something to make yourself safer.