This is a question for the lore team.

I can't find where it was mentioned (And with the reimage of the game in A Realm Reborn it could have been retconned.) but back in version 1.x of Final Fantasy XIV's lifetime I think it was mentioned that things like crystals and aetherial travel were exclusive to Eorzea. This, and the threat of the Primals which was why Garlemald was repelled at the Battle of Silvertear Falls in the beginning. One of the reasons Garlemald wanted Eorzea was for the concentrated sources of aether in the realm. However with Heavensward we have seen an introduction to aetherytes in different places including ancient places no man has visited in centuries. Now it's fair to believe maybe the Allagans first utilized this technology. This is further supported by the fact if I remember there was an NPC in Ul'dah by the aetheryte pre-Calamity who commented about it.

Nobody knew where the aetherytes came from or how they worked thus couldn't repair them if they ever broke. I'm going to guess after the Calamity somebody DID figure it out likely after Allagan relics started to show up more frequently. However with Stormblood now revealing that we will be traveling to Othard which is all the way on the opposite side of Garlean territory it occured to me if aetherytes are all over Hydaelyn. So bearers of all knowledge and lore, do aetherytes exist everywhere or only in Eorzea?