When I was in food service, it was (and probably still is) against the law to, for lack of a better word, "reuse" the food.
Employees could get fired if they took leftovers at the end of the evening, the business couldn't take a chance legally.
Which was a real shame because we threw away a lot of very good food, and a lot of employees were poor people.
Food service is one thing, but events outside the restaurant are entirely different. A lot of stuff gets lost on the way out the door to the dumpster.