A closed day removes every scheduling constraint at once
Most of the compromises in an office schedule exist because people are present or about to be. Floors have to dry before anyone walks on them, furniture cannot be moved and left, equipment noise has to be considered, and access to particular rooms depends on who is using them. A closed day removes all of those constraints simultaneously, which is a rare position for any premises to be in.
That makes it the obvious home for anything awkward. Moving desks to treat the carpet beneath, working at height over a work area, treating a hard floor and allowing it to cure, and giving a kitchen the sort of attention that involves emptying and cleaning behind appliances are all straightforward on a closed day and genuinely difficult on any other.
