Unlike a lot of robes, the Black Leather Robes do not grant the Wizard's Endurance perk.
Technically, the armor isn't robes. Robes are simply part of it.
This is one of the few clothing items in the game that allow undergarments.
Wearables are items that are worn to boost or lower stats. They are different from weapons due to the fact that they are not directly used to hit the opponent, or that hitting the opponent is not their primary purpose. Rather, they aid combat in other ways.