In one of the books it's mentioned that simulations have moral component.

If you simulate conscious entities at the level of detail that Culture AIs are capable of you create sentient virtual beings and you can't just shut down the simulation without being responsible of "murdering" sentient beings.

So if the minds simulate alternate universes in infinite fun space I think they are purely mathematical universes devoid of sentient life to make the whole thing less contentious and purely fun.