Even before this returning trays implementation, my wife and I had always been well disciplined at hawker centres. We will stack our bowls, plates and utensils together and use tissue papers to wipe dry our areas before leaving the place.
Once I was in a Jakarta KFC restaurant. When I walked to clear my trays and chicken bones, those sitting nearby to the tray return bin were very surprised to see what I was doing. I think to them, it is not necessary to do as such. However, I had been to Japan during my working years and had already picked up this good habit from them. Even when I was training in Italy, those Italians in their food courts practice the same.