In reply to ianstevens:
I used to think the same about there often not being a need, then I had an accident where I took a huge lob, flipped upside down, hit the wall back first, closely followed by the back of my head. Thankfully, for reasons unknown I had decided I would wear my lid that day and so I was fine. Got given a cup of coffee, then got back on the route. Had my head taken a whack like that sans helmet that may have been the last time I ever climbed.
Saw a similar fall just a couple of weeks ago in Kalymnos, very experienced climber, helmet smashed to pieces but it being on his head meant my mate needed a beer and a sit down instead of a helicopter.
These situations are rare, mine and the one I saw a couple of weeks ago are the only ones I’ve seen in 10+ years but in both cases our helmets absolutely saved our bacon and we were really, really relieved we had them on.
I’ll never climb outdoors without a lid on, and although it’s a matter of personal choice, I’d always encourage others to do the same.