It's been talked about before and in the end it was decided that it was a balancing thing. Wizards, Sorcerers, Rogues, Druids, ect. can't equip it without the feat which makes for player interaction via trading for CNR resources. Doesn't stop whimpy wizards from mining with the feat, but it comes at a price. I do agree that it shouldn't take the feat, but it can pretty much be argued either way to a stale mate.
