Serious question: Why does it not help the server in an informal restaurant if the dishes are stacked at the end of the table (esp at a booth)? I would have assumed that it was a "nice " gesture. ( From the "old days" when properly brought up young people were taught "not to make extra work for the servants".)

Of course in a more formal restaurant one assumes that the bus people will remove the used dishes at just the right time and in the most aesthecitally pleasing manner and that for the guest to "stack" them on the table would be simply to destroy the beauty of the table and the dining pleasure of the other guests. I assume it is in that sense that you find it rude to the other people at the table and in the restaurant.