It's a fuckery thing. I don't know if it is in some adopted bylaws or not, but it's not in the Constitution so I don't really consider it more than a tradition or custom that can be disposed of at will.
But… You have a room of 100 people and various complexes around them who treat it as real, so until some executive or judicial force is applied to get rid of it or people are elected/appointed who don't believe in it - it's real enough to them.