Most of the time it is because players, don't know what they're doing and when they're wrong they don't always know it. Plus it's not like if zor was going to meet every GP in real life so that he could have an idea of if the person will abuse of his powers or if he'll be the dog of the staff(which is not an insult, dogs are animals with an high sense of loyalty, a pretty great example:Hachi).
So it is to make sure that Gp don't make mistake, but also to be able to close the discussion between should or shouldn't you be banned.