When a sandwich/ice cream/big mac artist concedes to this, its most likely because they've already rung you up and don't want to go through the hassle of cancel

When a sandwich/ice cream/big mac artist concedes to this, its most likely because they've already rung you up and don't want to go through the hassle of canceling the order and then re-inputting it correctly. I don't get the logical leap from vendor to customer here. Impulse purchases are not exactly the same as an underpaid worker not wanting to have to deal with a hassle. It's still a valid technique for getting what you want, but not directly applicable when you are the seller.