First, let me answer the obvious question of "why?" My response, "for convenience."
Now, I've got that out of the way, I am sharing an interesting experience I had. I usually use Hogson Mills Buttermilk Whole Wheat Pancake batter mix, which I find is satsifying, supplying me with a nice flavor, good texture, and healthy ingredients (few of them!). I do add a few other ingredients to the mix to jazz it up even more, but I find I can eat the pancakes plain, too. I normally add powdered ginger and plop frozen blueberries into the batter once in the pan. Cinnamon also adds nice flavor. Pure maple syrup and butter completes the orgy.
I didn't see this boxed mix so I bought their "Insta-Bake" which can be used for making pancakes as well as other baked items such as cookies, brownies, waffles, and biscuits. I read the ingredients to see what the difference was between this and the pancake batter mix. The major difference I saw was the absence of dextrose and corn flour/meal, but the addition of sweet whey and wheat starch.
The first time I made the pancakes I left out the sugar in the recipe thinking that maple syrup would supply the sweetness. The cakes tasted flat, more like a biscuit, and had a different texture from that of the other mix - it was more moist and not as crunchy. The next time I made the pancakes, I added some corn flour to the flour mixture as well as sugar, and the batter tasted better. But it still tasted more biscuit like than the other mix that Hodgson Mills makes. It got me thinking, if a person was making pancakes from their own flour mixture, if it would taste more like the "Insta-Bake" version or that of the "Buttermilk Whole Wheat Pancake" mix.
I liked both versions, but I am more used to the "Buttermilk Whole Wheat Pancake" mix, in that it has a crunchier and richer taste. The batter also has a crispier exterior. I wonder if the presence of sweet whey and the wheat starch tend to keep the batter more moist than the other version. There seemed to be more space between the batter particles when done than the Insta-Bake version that had more of a cake/biscuit-like texture. All other ingredients seemed similar (i.e. whole wheat to enriched flour ratio, leavening, salt, buttermilk solids, etc.) other than the absence of corn flour/meal and dextrose. I do like the presence of some of the corn meal to balance out the wheat flour. It's almost like in the Insta-Bake mix, Hodgson Mills has supplied the baker with just the very basics, allowing him/her to modify the mix, namely to build from a basic foundation, which is what I began to do. (I will eventually try their Multigrain Flaxseed Pancake Batter mix which looks very interesting and healthy!!)
I have tried other versions of pancake batter mix, including that of Arrowhead Mills, and so far, I prefer the taste and texture of Hodgson Mills mix. Most of the ingredients in the mixes of other companies produce a different kind of pancake, and I needn't go into the quality of the ingredients, other than to say that the result tends to be a low fiber, high carbohydrate, high fat product.