The thing is, this is just something to screw around with and people want, If you don't want it than just don't do it, only 'real' reason would be harassment but again that's easy to avoid.

Doing it in restricted areas takes the fun out of it as well, half the fun of dueling is being able to make your arena within the games world. Restricted areas or not there isn't a real reason for it not to be added, not something intended to earn tomes or prizes with anyway.