As a rule it's my face that hits the snow/ice hard and not my head so unless I went for a full face guard it seems it'd do little. Besides a little danger in life makes it worth living
Probably the biggest reason though is while I'm happy to wear the most stupid/outrageous hats I can find, wearing a hemlet seems to be going too far. I've yet to see someone who's not chucking himself down an almost vertical drop from a helicopter who doesn't look daft in one.
It was this guys reaction though that I found odd. He thought it crazy not to wear one even on groomed piste.