The order in which Jobs get their abilities hails back to a time when they thought the Jobs would be more diverse than they are. They built quests around earning these abilities and some of those quests would no longer make sense without them. Oops!

They should still make AOEs all come in at the same levels for every Job. Maybe it can differ by role, but not by Job. And DRK not getting the end of its AOE until 72 is ridiculous. They should change it in Endwalker but apparently they're not going to. It's just silly.