yeah i hear you both, you even get people saying 'its better than nothing' that, in some cases may be true, but alas, not when it come to your head.
when i was running the local kite buggy and landboard club, it was hard to enforce any rules as i was the only one doing any enforcing, and people just dont like to be told what to do.
when its on a public beach, looking as if you care about safety can reassure others they are safe with you around, others look and say 'if he is wearing a helmet it cant be safe'.
running a formal event allows rules to be laid down and adhered to.
meeting on a public beach for a social sail, leaves those who ask you to wear a helmet, open to ridicule, and sometimes even aggression. people come back with things like 'its not your beach' and 'who made you boss around here' and so on.