It's been said before many many times and it will be repeated here. For SE to get rid of the Class System and replace it with a Job System everything that the Class system touches would have to be re-calibrated. Buildings in cities, NPCs and dialogue in the game, the lore of the game itself, and not to mention we'd all be reset back to square one making whatever you accomplished in this game moot. Crafting is part of this Class System as well, and with a Job System that would be relegated back to the crafting system of XI. A system that most people don't like and hardly use. SE adding this Job System to go alongside the Class System is their way of appeasing the group that's been crying/shouting/screaming/annoying for it to be put in place.