I just convinced my dad to wear one! He's always been a hardass and at 54, it hasn't got any easier to convince him that he isn't superman. His logic is that he lives on an island in Florida, inhabited by very old people, and the speed limit on the entire island is 35.
I said, stand perfectly straight and fall forward using nothing but your face to break the fall. That's under 10 miles per hour. Now go clean yourself up and when you're capable to speak again, tell me that you're not going to wear a helmet.
He has a black helmet now... I think I'm going to buy him a white 3/4 with lots of vents for the hot weather for father's day.