There isn't really an explanation, other than gameplay wise it's to make it so that you don't go up there regularly, until you find a reasonable method to obtain passes. The idea is that there's so much traffic, and that's why they're so hard to get.
that is counter intuitive, if there is a lot of traffic it means there is a lot that are getting the passes then, while sure supply isn't matching demand, but many are still getting in. at the very least there should be a seller of the real passes then. it sounds like you intend there to be a more permeant way up in the future. or your talking about the tinker option with the passes. kind of odd but ok, though there isnt exactly all that much up there now, but its a bit tedious when hunting for the new content after a update.