Note sure why the food court would need to stay open 24 hours. There is no McD's in the convention center food court. Maybe some time ago there was, but it is no longer there.

Also, last time I was there it seemed that half the restaurants in the food court were closed.

Guess it depends on when you went to the food court. Since they are a business, if they feel they are not getting enough customers, they will close down for the night.