Demos are a wierd beastie.
As it was related to me by the previous SocSen, someone threw a fit about allowing "mundanes" to fight in armour at renfest like demos, so that was made illegal. Someone found a loophole and started "whack-a-knight." Someone else threw a fit about that not being within the spirit of the rule, so that was made illegal. Someone decided that they would just have people sign a waiver, declare it a fighter practice, and then work with the public. Again, someone threw a fit and that was made illegal.