It's frowned upon to take more than you need.
Bob is at a buffet restaurant and heads over to the buffet area.
Bob wants to get bring food back to his table.
Bob takes only as much food as he will eat to his table.
Bob piles up a huge amount of food and takes it all back to his table but only eats a small portion of what he took.
The employees are glad that they don't have to throw away a bunch of food since Bob didn't waste any.
The workers at the buffet have to clean up after Bob, throwing away all the food he wasted.