At the MD Ren Faire, swords of any kind are no longer allowed, apparently. It used to be namely sharps, blunts or anything that resembled or could be used as a weapon. Sirs Edward and Brian had found a 'workaround' - scabbards filled with oddments of steel and/or lead and epoxy and topped with a guard, handle and pommel so that it looked like you were bearing a sword when in reality you were not. At least not one that could be drawn, and that was usually good enough for the ones running the Faire.
Which is not so much weird as odd- the VA one, which is less than 100 miles south allows weapons, so long as they are peace-tied you can carry them (pistol and other gun replicas do not apply here).
To answer your question as to why they do not allow them, Sir Edward or Sir Wolf can best explain it as they're the ones who have been going the longest and call tell you about some of the shenanigans that went on 'after hours' - drunken duels done with sharps and the like which caused the Faire promoters to enact the no-weapon clause, costume or real.