To-go boxes aren't as much of a thing over here in the UK. We do call them 'doggy bags' - or at least I do. Maybe that's just something I learned from my parents and have applied to the disgust of everyone else in society.

Either way, they're normally only deployed if you've got a substantial amount left on your plate, or you've mistimed your meal and have to leave early. I can imagine my grandmother recoiling in horror at the idea of anyone thinking we were too poor to leave food we didn't want.