On this site, Outsider is used to represent anyone that isn't appart of the RPG (which is what this site was built for). And techically, if you're not inside the RPG, then you're outside of it (case and point)
It is much easier to use that to continually say "non-rpg memebers" and I think the word sounds a lot better as well; and it perfectly represents site visitors, because if you haven't yet been trapped on New Genesis, then you really are an outsider...