I think the Boomer "Eat all the food on your plate" meme came from their parents, who lived through the Great Depression and food insecurity. Mindlessly passed down from a time of scarcity to a time of abundance. They just repeated it, but this time with gigantic, obesity-levels of food on their kids' plates.

We usually just ask our kid how much she wants to eat. It seems to work a lot better than the way my parents did it, with a lot less drama, and she's not growing up with an antagonistic and/or compulsive attitude towards food.