Ralphie was raised to never leave an empty plate at meal time. To this day, he has a problem doing that and will finish no matter how full he gets sometimes. So I think it has to do with the brainwashing our parents put us through as kids.
For me, when I'm done eating, I'm done. I stop. Even if the plate's still full. That behavior came from be being a general pain in the a$s as a kid.
