It's rude to steal your colleagues' lunches.
Bob is at work when he realizes that he forgot to bring his lunch with him.
Bob wants to have something to eat.
Bob goes downstairs and orders food from the work cafeteria.
Bob takes some of the food from a coworkers lunch box in the office fridge.
Bob is full after eating his meal and remembers to bring his food to work the next day.
Bob is called into his boss's office and loses a day's worth of pay.