YANBU but having worked in Pizza Hut as a manager after graduating nearly 20 years ago you would not believe the level of pisstake from the customers. So when people ask for extra plates it makes you a bit wary.
More than likely someone has asked previously for a plate to share and filled it with a foot high pyramid of potato salad, coleslaw etc basically for free.
I've had people drink a whole bottle of wine and declare the last glass undrinkable, or try the evening when i had a complaint about a hair in a pizza crust, which happened to be the last 3 inches keft on customers plate. Hair on plate was 12 inches long and black. Customers hair was 12 inches long and black, i had short blonde hair and my kitchen supervisor who made the pizza had a shaved head!
Then the chap who tripped up a waiter carrying drinks by sticking his feet across the booth on a Saturday night, then insisted we pay for new shoes, as they had Tango on them. Then insisted they were Dolce & Gabbana! 
Oh and a "posh" customer who declared when presented with his bill, that he would not be paying for his finished meal, as he hadn't enjoyed it due to the cutlery being "too cold". (I kid ye not)
And believe me these customers didn't look dodgy at all, i've seen a well dressed family of 4 (two young kids) sit by the door and then do a runner without paying. Carrying their kids and charging down the street!
And you are measured on your margin so tightly in that company. (try having to count all the stock including straws at 5am on a Monday every week, then entering into a computer to ensure you aren't wasting product.) 
It all sits on the shoulders of the tiny team in the store, so they are always a bit wary.....
God I was glad to leave! 