To balance out the remaining eggs in an egg carton. Thus, creating even weight distribution.
Susan: Tom! You can't leave six eggs on one side of the carton and have nothing on the other side of the carton!
Susan: Because silly! You must acheive eggrilibruim. If you don't the carton will be unbalanced. Which will increase your chances of dropping it.
Tom: Ok...what would increase my chance of dropping you?
Susan: Oh Tom!