Because I like to craft stuff? At a bare minimum, being able to turn gems and gold nuggets into slightly less worthless vendor trash would be interesting.
Or for some added derp, make more lower-level, non-metal weapons and armor for crafting, to push back the real good shit to even higher tiers. Because once glass armor and weapons hit bandit loot level, things are getting silly.
Plus that gives me an excuse to find a use of bones and skulls. Adventurecraft in Oblivion when? o3o