After taking a look at the japanese slot machines, its obvious that there is no AI and its a simple touch activated script and animation, but what I am saying is that it would be way better to use AI. It would really liven up the gambling experience.
I think it might even work to the advantage of the gambling casino which owns such slot machines.
They could integrate some AI so the character on the slot machine could interact with the player according to the money they have won/loss or better they are having a bad or good streak. Perhaps, they could even play different kinds of music according to that as well, for example, an exciting/epic melody if they player is winning money (that may encourage them to continue playing).
Of course, all this would require a significant amount to money as investment and I am not sure if big casinos would get out their comfort zone in order to try something like this, considering they are already making money with classic slot machines.