I have seen on a door of a room "KEEP OUT". Apparently, they do not want people to enter the room.
But suddenly I reminded of other instances of "KEEP" being used as an positive imperative (rather than negative), such as "KEEP QUIET" instead of "DON'T MAKE NOISE" or "KEEP FIT" rather than "DON'T GET FAT". or "KEEP AWAY" rather than "DON'T COME CLOSER".
So, why make imperatives using the verb "KEEP OUT/CLEAR/FIT/AWAY etc." rather than saying the same thing "DON'T.....".