indeed, AI is popping up everywhere even universities are teaching it as students create basic robots that have the ability to learn.
The benefits of implementation in games is insane. Consider a game developer and the subject of complexity. while totally different games just bare with me for the sake of the conversation. On one hand you have Civ, which the developer believes that complexity needs to finite meaning for every mechanics he adds he tends to take one away. Paradox games seem limitless in complexity.
Both these games complexity are central to the games mechanics and how the player interacts with them. Now consider a AI that not only can learn but has memory i.e. a database that the developer implemented but also the AI might be able to add too.
The impact is nothing sort of monumental, a whole new level of complexity is added without the player having to learn more mechanics. Game mechanics work as normal players can theory-craft and make meta's but this is thwart by the AI as the more obvious you make it you're bee-lining a particular win the more power you give your opponents to identify and counter.
Consider how a player approaches the game now, they take say Korea and get a favorable start with plenty of jungle and food, they build tall and bee-line it over the course of the game gaining more of a advantage. AI now can be programmed to response to this however a smarter AI that can use memory (database) can make plays that are all about the bigger picture.
The AI identifies early the scientific power of your nation through the same means the players has to identify others. It lets you be. You continue building towards your victory but as you get closer and the congress forms the AI start to fight back. First response might be organizing a pack with other nations to take you down (each nation is independent so this could happen if another AI nation started to pull ahead it wouldn't be player vs 7 AI, they are targeting you simply because your the biggest threat for winning). They start equally taking control of city states in a bit to reduce the number you control, they don't have anywhere near the funds you do so they work together each getting 2 alliances each. Secondly with the delegates they have at the next summit they vote and pass a trade embargo on you crippling your ability to make and trade goods. Next while 2 nations may of worked and spent money on that the 3rd has been building an army and rather then try and concern you they identified one of your outlying cities owns 3 of the 5 luxury items and plan to not only take it but raise it too the ground as they are almost 100% certain through past experiences you will response and take it back.
Quite a long example. But lets recap, look how players and developers approach games now when asked how would you make the game more complex, most address sallow mechanics wanting to add more interactions or even new mechanics. Keep doing that and you get paradoxes games, that are extremely fun but also require an extreme amount of investment to learn. Something Sid Meier does not believe in. Now look at the impact AI can have. The player has nothing more to learn, all the player needs to know is to give the AI plenty of credit meaning if he telegraphs his intention such as in the example and gives himself only one way of wining the AI will lets him hang himself by letting him progress to the point of no return then smashing him into rubble.