Even riding a motorcycle without a helmet has externalities - more severe injuries from accidents could raise insurance rates across the board, and these people

Even riding a motorcycle without a helmet has externalities - more severe injuries from accidents could raise insurance rates across the board, and these people take from the ER/ICU capacity that others could use. I guess you could have a policy of just letting them die if they get into an accident without a helmet, but that its own host of problems.