I was raised to clean my plate "for the starving children in India". We were proud how well we cleaned our plates, regardless of how much was there, whether it was tasty or awful, or who had decided how much to put on it.
Of course, we weren't allowed to put on our plates only what we were hungry for. They had to be heaped high with food. It was a point of pride how much food we were able to pack down.
How'd that work out for starving kids in India, Mom? Didn't work out so well for me.