[throwaway3286]

What if they ran the simulation for too long, and accidentally created advanced life? Ethically they would be forced to continue to run it, otherwise they would be committing murder.

As a consequence, their government may have banned these types of simulations, to avoid the responsibility of keeping it alive until life is extinct. We are one of the few simulations that are still running

If they simply created us by mistake, we may be very different from what they are. Even the laws of physics could be different.

It would explain the Fermi paradox. They could be stopping advanced life to evolve on other planets, as they want to reduce the scope of the simulation. They created us by mistake and are waiting for advanced life on this planet to become extinct, so that they can finally shut down the expensive simulation.