I am by no means a Halo fan anymore ( long story ). But if the game takes place in a sandy region the the cape would fit. Sand is devious and gets every where but the cape would only protect the upper joints. If it's a cold a region then the cape would help protect the upper body from cold. See all that metal near the heart in the cold can be deadly. So the cape would be used to retain heat. But your probably right...it's just copy of their creators. Lazy!