We do use the room service a lot, 2-3 times a day if DW is along. After a few days the waiters on RS duty know me and get my orders quickly as they like the tip. So we generate a lot of trays.
I too don't care to see all the trays in the passageway, but Mike is right. You are supposed to call room service when you need a pick up. Of course, they say 'thanks-place it outside your door'. So that's where they are supposed to be. I don't mind so much as I don't like to see trays in my cabin either, but because we have so many I do tend to leave some for the cabin steward as well.