Thanks Han
Its totally personal (i don't always wear one rock climbing) - but with my bike i always ,think well i've got one, may as well put it on. If you're doing a hot ascent you can always put it on your bars, and you can get nicely vented ones these days. won't help if you get flattened by a bus, but mighty handy for any contact with road or curb (which can happen in quite a lot of ways!).