It may or may not be healthier, but the subjective taste preferences of the masses is pretty much settled fact at this point.
Frosting is a different topic - totally agree there, but I haven't seen any blind taste tests on that one.
The professional bakers around me who do a dozen cakes a day or whatnot are all pre-made mixes, maybe some small modifications to the mix, and from-scratch frostings. I'm not sure I could even find a local spot with cakes made from scratch - at least in the traditional sense. The spots making 200 cakes a day perhaps, but those are going to look a lot more like the mixes you buy from Sysco or whatnot.