People said that to me a lot when I was a kid and I took a very long time (only once a teenager or adult?) to understand what they even meant by that (how was that sentence going to make me eat?).
It even had the opposite effect, I was like: cool a solution: less for me, more for them, and everyone's happy!
Even now that I get the thought, I still think this is a nonsensical sentence to convince people they should eat things they don't want to.
well besides it being a bad way to convice somebody
for me, it is not about wanting to and its not about childhood(I am an adult and I still strugle + am told what a awful person I am for wasting food), I have a small selection of gland foods I can eat in comfort, everything else is unbearable to eat, I don't refuse food because I don't want to be nice and just eat up, I refuse because It is painful to do and might vomit it all back up again