There has been a recent trend of online games which actually just use bots. It took people a very long time to notice. I think the purpose in these sorts of games is to make the player feel they are more competent than they are (how often would you expect to win in a real 12 person lobby?), but they could also be used to more nefarious ends.

https://www.youtube.com/watch?v=YCqnD40Q5T8