In many multiplayer games often times players are replaced by A.I. controlled players in situations where a player may have dropped from the game or the game was created without the required number of players. This allows players to continue playing their game but it can also lead to a lot of frustration in situations where the A.I. player feels useless due to not really playing with the team or making what would be considered a wise decision. Games that allow a degree of control over these players decrease that frustration substantially and creates a more pleasant gaming experience.
Example 1: Heroes of the Stom
Often times in MOBAs a loss of one player typically results in a loss for that team. Blizzard in an attempt to give that team a fighting chance replaces the missing player with an A.I. controlled version of their selected hero. On top of the replacement Blizzard also allows any one on the team to give the A.I. simple commands such as to follow them or to attack certain objectives/structures/enemies. While the A.I. doesn't really have the same level of skill as a player, this inclusion of control over the A.I. at least gives the team a fighting chance to still win the game.
Example 2: League of Legends
In League, the player is able to choose which difficulty of A.I. that the player wants to face. There is an Intro A.I, which runs through basic mechanics for new players, beginner A.I, which is a little bit more advanced, then Intermediate A.I, which is a bit smarter, and will react better towards your spells. These different tiers of difficulty allow players to increase their skills, and feel more in control of their gameplay experience.