(1) It's considered to be a "Classical" dance, and as such they try to keep it true to its fundamental nature. To some degree that's actually inconsistent, because the steps themselves are not exactly the same as the original, or "Vintage" Waltz steps, but the basic concept is there.

When Waltz was first danced, you had Natural Turns. A little time later, there were Reverse turns. Sometimes they turned on the spot. But that was about it. That's what the original Waltz was really all about, and that's how they want to keep it.

(2) One of the nice things about Viennese is the look of the dance floor as a whole. There is a consistent flow and elegance to it. This is due to the fact that the dancers all move and turn at approximately the same speed, if not all in the same direction. Once you introduce alternative patterns, especially those that move against the line of dance, or those that stop to create a line, the classic look of a Viennese floor is lost.

(3) Viennese is the only real compulsory dance in competition, and it gives the judges a really good chance to compare the dancers on an identical level. Some people claim that Int'l Latin should have a compulsory dance, too, although I'm not sure which Latin dance would be most appropriate. Paso, maybe, since it is the most "classical" of all, and since it uses the same music with the same breaks. But I don't expect that will ever really happen.

(4) Probably the biggest reason: Bureaucracy. Just try to talk those huge egos at the top into changing anything. It'll never happen. For years I've been trying to tell them that they're wrong about Jive rhythm (3/4, 1/4, whole), but the only thing that gets me is lower exam scores.

I hope that sort of answers your question. Remember that none of those reasons apply to social or American style Viennese, so by all means, do what you like. I encourage it. Just be aware that the rules change when you dance for an examiner, or at a competition.

Sincerely,
Jonathan Atkinson