I actually a friend do that in our house.
Now, we were poor college kids home for a break. We had dessert (I don't remember what, but it was some sort of cake/pie/something eaten off a plate with a fork). She ate the dessert, then licked her plate. Now, she usually displayed such polite manners, so I was shocked to see this. I blurted out something (rude), like, "if you're still hungry, there's more. Help yourself!". She replied that she wanted to savor every bite since she doesn't usually eat dessert. I was in total shock!