The goals are very different. AI in games needs to provide a challenge to the player whilst still being comprehensible. Most of all it's designed to be beatable

The goals are very different. AI in games needs to provide a challenge to the player whilst still being comprehensible. Most of all it's designed to be beatable. Part of the reason games make a good deep learning challenge is that they are consistent systems that people can comprehend and reason about pretty easily. Most FPS games with the exception of titles like Alien: Isolation simply haven't needed anything complex. Essentially more complex AI with the same freedom wouldn't be noticed by the player in most FPS games. Given more freedom a more complex AI suffers from being less comprehensible as the player is less aware or unaware of the actions it took to do something clever. For example a clever enemy that flanks the player is experientially identical to a scripted event that spawns dumb enemies on the players flank. Further the advantage to the second technique is not only that the AI requires less work but the entire scenario can be carefully designed. Which is not to say a more intelligent AI wouldn't make for a fun FPS game it's just people haven't been making those games.