Comment by breuleux

Depending on capabilities within the simulation, that method scales unpredictably. If you can build supercomputers and run programs on them, these need to be simulated accurately at all times lest it becomes noticeable that they don't perform according to spec. Basically, the more machines you build, the larger the set of interactions that must be simulated becomes, and if your simulator's capacity is limited, then either things have to break from the perspective of the simulation, or the simulatees are effectively performing a denial of service attack on the simulator.