Why is some orn-increasing equipment locked to mage class only?

I have a dark mage hood and a reaper's robe I've been using while farming for orns as a majestic. After upgrading to battlemaster, I can't equip those pieces of equipment anymore.

Is there a specific reason that the orn-increasing equipment is mage only?

I think you should open up the equipment to all classes or add orn-increasing equipment for the other classes.

Does anyone else have any thoughts on this?