Why are you splitting armour pieces apart / removing them?

[The Waiter]

I don't get why the devs in charge of adding items to the game don't put in armour pieces of a set, such as the helmet of the bear armour which is restricted to NPCs only for no reason. Or the sturmhaube helmets which were supposed to be for the striped armour but split apart by class requirements.
Another good example would be the helmets of both gothic plates. Which both exist in the game yet are unable to be bought/crafted/looted.