Since salt is cheap, a lot of commercial rubs list salt near the top of the ingredient list. Sugar is what caramelizes and gives you great bark. Because I had a very large (8 butt) cook, I ordered Bad Bryons Butt Rub and mixed it 50/50 with sugar in the raw. It was good stuff and received nothing but compliments. Personally, I like the bark from having brown sugar as part of the rub.