I'll add to your theory because I think it's a damn good one. Access to Antartica is almost impossible without being able to take military planes and even if you do you are only allowed on the edges. No international flights go over which can be argued. For some reason all the masons get to visit the interior like Buzz Aldren and bonesman Kerry. I suspect there are probably ruins that they don't want the public to know about because we would have to revise the limited worldview...