Originally Posted by
Physic
its just because, lets say that while you have an item equiped you get attachment, and you have some good item that you want to add materia too, The system would encourage you to wear the gear that needed to level, and not the one that you wanted to make powerful.
hence you would be using your gimped attachment gear most of the time rather than your god armor of the heavens. It makes a lot of sense while your leveling, to give your new gear some boost from your old, but high level, it means wear gimp gear, equip god gear for boss only maybe.
soooo they got to figure how to balance that urge