I always wondered why the FUCK waiters/bussers do this until I got part time catering work
the answer is bosses have this brain worm that makes them believe that a plate with a single bite taken out of it being in view of a customer makes the customer angry and likely to complain that tHeIr TaBLe iS dIrTy
the worst part is the bosses are correct, 1% of customers do in fact bitch and moan if a plate full of food they decided they're not interested in isn't telepathically recognized by the busser as unwanted and whisked away 0.5 nanoseconds after the last desired bite has been taken from it
and so because of these fucking psychopaths, those of us that want to finish our fucking fries have to guard the plate like a starving dog ๐ซฉ