The point is spellcasting allows players to trivialize the Lockpicking skill and get around durability loss penalty when blasting past locks.
Using that repair hammer takes points in the Blacksmithing skill. That creates a cost to using it.
You can get items with +blacksmithing to use a repair hammer.
You can get items with infinite durability if you're lazy.
Also making blacksmithing infinitely better than lockpicking because it's lockpicking + crafting other items isn't exactly fair either.
