No reason except it doesn't seem to keep as well as the acid, and some recipes call for the acid. If you decide some day to play with stock solutions in glycol or TEA, the ascorbate will not dissolve but the acid will. I find it more convenient to have a container of ascorbic acid and one of baking soda than one of ascorbic acid and one of sodium ascorbate. Besides, when things don't go right, the baking soda helps the ensuing gastric disturbance, so I need the baking soda anyway.
Originally Posted by chakra