Depending on the game, it may be done on purpose.
As someone who's made games, released them, and suffered so many complaints about how hard they were, so I'd dumb down the A.I. and still get complaints about how hard it is.
Or another 2 player turn based game that included three different difficulties and had a ton of people telling me easy mode -- which was basically the computer making random moves -- was impossible to beat, and the computer cheated, and the game was stupid, and I should kill myself for making such a stupid game.
A.I. isn't usually super great in games because it doesn't have to be to give a challenge to the vast majority of people.