Oh. Well, I guess in that scenario, they're the ultimate gatekeepers to all of the various servers around the world.

Like, depending on where you are in the world and where your destination server is, if you're both on different Tier 3s, you have to go through your 3 to a 2 then a 1, then back down to a 2 that leads to the 3 where your destination server is. If a Tier 3 says "you shall not pass", but the 2s and 1s say it's okay, you can just get a new 3 to access the 2s and 1s. If the 2s say no, it's a little more difficult to get a new 2 to get to the 1s. But if the 1s say nay, you're kinda screwed.