User blog comment:Norman-123/Tactical Idiocy in Halo: Episode 1: WHY IS HALO 3 SO HARD!!!/@comment-4791684-20100625024415

Heh, Halo 3 isn't hard. Even on Legendary it's easier than Halo 2's (having completed both on Legendary, I speak from personal experience).

Simple answer: Bungie wants to make that part a game and can't think of a reason why. But it's another point of why Halo 3, on top of being repetitive and unrealistic, fails.