Is it really possible no one instructed them to wear life jackets? Or is it more likely he typically wanted to prove everyone wrong? Obedience is taught to instill discipline. Sounds like Kevin already had plenty of discipline, yet apparently self-taught himself to never listen to anyone. Sounds like a combination of both Daedalus and Icarus.
The trick with helmets is when the risk takers are wearing them. Then wearing a helmet can become a signal you ride hard.
I think that’s a good part of why helmets took over skiing in Colorado but not California. In Colorado, the extreme skiers wore them, and the rest followed.