Riding in the rain tonight, I was having a great 'ol time, of course paying attention to traffic, but also paying more attention to the splashing water than I should have and didn't notice that the rain had weighted down some branches by the side of the road. Got a good start when they brushed over the top of my helmet and was glad it wasn't my scalp. Ouch.
So, the helmet is to protect my stupid, inattentive brain.