Why would it be unethical or illegal? You are also basing the fact that the simulation is run by humans or any other entities with a social structure and a grasp on what we call "morality".

If we are living in a simulation morally it is not much different than the SIMS or minecraft...

Downloading pirated torrent is unethical and probably illegal, but tons of people still use it. So I think "less likely" is not really the case. People will do anything as long as there's value.