If you are expected to be a GM 4+ hours a day, and you are not allowed to have any fun with any regular accounts, nor are you allowed to socialize with other players, then sure, there SHOULD be some pay involved for asking for those sacrifices.
But I do think most GMs were (ideally) previous players who cared a lot for the server, hence they have relationships with others, and do most of their GM work from dedication, and free time, an thus, should not be as limited by rules as in the previous paragraph.