From a discussion on Q23 about the “rubberbanding AI” in Oblivion (aka levelled lists of mobs):

—

Gordon Cameroon:
How cool would it be if you stride into a dungeon and all the rats flee from your path like a sinking ship?

Here’s the thing though: the game is built around hack ‘n slash. Fleeing, while a realistic and impressive action for intelligent mobs to take in the presence of a hostile enemy, goes against the policy of making it easy for the player to kill shit. So now its “make it easy for the player to chase after shit?”

And since the mobs respawn (or get replaced by better monsters through no action of their own), should it even matter to the mob if he’s killed? Regardless of what happens to Mud Crab #324, Mud Crab #325 will be there again soon enough. They must be ecstatic you came along to allow them the one pleasure in their life: attempted killing. I mean, a 30 foot perpetual walking patrol only brings so much delight. For most mobs, you’re the only thing they’ll ever fight, and besides walking, standing, and making a simple sound, trying to kill you is the only thing they’ll ever DO in the game. I guess fleeing from you with the possibility of trying to kill you later is a step up, though. But attacking you *nearly guarantees* either the glory of causing you to reload or the unique event (relatively speaking) of their own death… fleeing is not as impressive and if they flee from you they may never see you again.

Mud Crab #646 at Location #49043: “Wow, of all places in the world he could be the hero is here, right HERE! My one shot at glory! Haha… maybe he’ll be AFK!… SKEEEET! (Mud Crab battle cry)

*Plunk* (ok, maybe not AFK).