My personal theory is this: Garleans were obviously created by the Ascians (Ancients) probably in response to how events played out with the fall of the Allagan empire.

Emet and the other unsundered would have the foresight to see where they may have gone astray with the Allagans and course adjusted for Allagan empire 2.0. Remember Ancient's whole civilization was centered on creation magic.

Also correct me if I'm wrong, but Azys Lla was shown to be creation point for all of the beast tribes. If I had to make an educated guess, I'd say the Ascians when creating the Garlean empire decided to cut them off from aether to prevent the new civilization they were building from aspiring to attain what the Ancients were (which is what the Allagans were probably close to achieving).

The Ascians obviously want an empire in place to use as pawn to create calamities and rejoinings. But its no good when that pawn seeks to take the place of your old civilization and/or follows down a path that will make the same mistakes as your ancient civilization.

To further this thought process and looking ahead to the story, I see a lot of people hoping we get echoed to past events involving our characters back story as Azim. What I think we'll see and, this will most likely be major plot point of 6.0, that we have been reincarnated numerous times corresponding to all the calamities. I would expect a reveal of us, in someone else's body, trying and failing the stop the war between Allagans and Mercaydia, essentially filling in our back story and giving a better explanation of history in general.