Cupid & flor, you are both right. However, in USA (maybe some other countries too), they get used to clean their table after dining in a fastfood chain but not in a fine dining restaurant. You will never see anyone leaving their mess in the table after they eat. That is their culture.

In middle east, it is being practiced in Ikea restaurant. You have to clean your table before leaving in exchange for the cheaper price offered for their foods.