So... when are you guys going to stop arguing?
Both sides of this debate have made their points, and the bottom line is that a given resort will decide its own helmet requirements.
If you see someone else without a helmet- it doesn't matter.
If you see someone else with a helmet- again, it doesn't matter.
If a person who refuses to wear a helmet has an accident, let Snow Patrol worry about that.
If it's your best friend refusing to wear a helmet... just let them know your personal concern for them and maybe they'll change their mind. Otherwise, let them be.