Now, sure, Master Chief is seven feet tall and weighs quite a bit in his armor, and yes there are occasions when, under my guidance, he has jumped off cliffs or bridges or buildings of his own free will or carelessness. Still, a basic OSHA inspection of USMC or Covenant facilities would turn up glaring omissions of basic safety precautions.
(And from a game-player's standpoint it's real drag to have to replay a tough level just because you accidentally walk off a bridge when you're not looking.)