People are fighting on plaza because there is the spawn point. By this you can meet (kill for some ppl) there more people at one time than in other places. Also when you die in a duel, Plaza is the place where you move from death realm.
Maybe when things will be like it was explained in the first official news about death realm and you will appear back in the world of living, there where your soul left the body, it will be easier to move fights to another place. Maybe to arena, where these should take place.
For now, even if someone want to fight in arena, he won\'t, because when he/she die, He/she will have to run all the way back to arena. What for if you can fight at plaza?
I\'m always looking for realism when looking for solution of any problem and i don\'t see it in this topic. Also turning auto declining duels isn\'t good solution because people shouldn\'t fight at the city plaza, which should be the place of trade.