And are there any regulations on it?
1 - There are aetherytes in almost every town and outpost, even small ones, so presumably they are commonly used, but that being the case why do most people not seem to use them? I get it for merchants with carts and such, but even regular people always walk or take boats or airships everywhere. What was stopping the older Ala Mhigans from just teleporting back to Ala Ghana? Does it require an amount of skill in aetherial manipulation that most people don't have? In that case why bother having aetherytes everywhere?
2 - How fast is it. In game we see it as instant because, well, as a gameplay mechanic it has to be, but is it instant in the lore? In the latest MSQ Cid says: "Time no doubt being of the essence, could I tempt you to a ride aboard the Excelsior? If there's a faster way to Raubahn's side, I will personally apologize to the commander for keeping him waiting." Wait, really? Your airship can get me from Mor Dhona to Ala Mhigo faster than a teleport? What's the point of teleports then?
3 - How is something like teleportation regulated? If anyone can just attune to any aetheryte what's stopping people from going wherever they want whenever they want? What does the Ul'dahn checkpoint do if anyone who's been to the city even once can just teleport back, ignoring the gates and guards? Are the main aetheryte plazas in every city heavily guarded and we just don't see it in game?