Every hotel has different requirements and different rules and regulations. Generally, hotels will specially prepare various working meals for employees, so that employees can choose for themselves. There are also some small restaurants, which will directly cook working meals for the waiters with the better meals left by the guests.
From a sanitary point of view, some people who come to restaurants may have some diseases, and the food eaten by sick guests may infect hotel staff, so not eating leftovers from guests will have greater protection for the health of staff.