I've worn one since about 2003. Apart from keeping my skull intact, it keeps my head warm.

Some dozy bint turned around with skis over her shoulder and clobbered me on the back of the head outside a restaurant a few years ago. Fortunately it was just a flesh wound but it could have been more serious. Unfortunately I was carrying my helmet under my arm at the time as we were just about to go for lunch and I wasn't expecting any major ski accident between the ski stands and the restaurant.