They've talked at length about this before, so we know that they DID consider whether or not it could fit in XIV, or whether or not they should change it to add it as a traditional job/class to fit XIV, with the preference being that it be added as the true Blue Mage, and not a version that "learns" abilities once via quests and plays like the other casters in this game.
Clearly this is their decision, that they did not want to change it to fit the traditional job role, and so rather than leave it out are adding a new set of content designed specifically for it so they can add it under it's traditional design.
Honestly, some of ya'll are being really narrow minded about how classes can be added to a game like this.