Why interned warships retain caretaker crews

Why were crews left aboard interned ships such as the German High Seas Fleet?

A caretaker crew kept each disabled ship safe and maintained while avoiding a large maintenance burden for the detaining navy.

Internment disables a ship in a reversible way rather than transferring it outright as a prize. A reduced crew keeps the vessel afloat and maintained while most personnel are accommodated ashore or sent home. For the High Seas Fleet, this also spared the Royal Navy from taking responsibility for maintaining a large collection of German ships.