At home I generally clean my plate, but I only take what I think I will eat. At restaurants I usually have leftovers. Growing up my mom hated waste, so we took a small portion, and then if we were still hungry we took seconds. We were never forced to clean our plates ever as children. For the most part I think it borders on abuse. Being force fed is disgusting. I understand some children are testing their parents or being stubborn, but hear too many stories of kids truly hating a particular food and having to swallow it, sitting at a table for hours. That would have been torture for me when I was young. I would have hated my parents beyond belief and probably never have forgiven them for it. I have a very strong gag reflex, and am phobic about gagging and throwing up, and one morsel too much and I felt nauseas, and would be freaked! Making me eat something I hated when I was little was on the level of threatening to push pins in the bottom of my feet.
People dismiss people like me who are afraid of throwing up, who cannot swallow pills easily, who need to leave the three bites on their plate, as being dramatic, or that it is all psychological, but it isn’t. We actually anatomically have a stronger gag reflux, I probably have more taste buds than average, so flavors are more intense (in fact children have many more than adults, and that is part of the reason they typically don’t like strong tasing foods) so it is a real thing.
As I have become older, I can eat more, unfortunately, but I still never want to eat so much I feel sick, or ever want to eat anything that tastes disgusting.