I expect certain sauces or complex recipes (e.g. soups, pies) to be premade to preserve consistency across locations, but really, if you're offering mashed potatoes as a side item, I should be able to taste chunks of mashed potato in my mashed potatoes.
The first time I sent my kids off to overnight summer camp they were served up dehydrated mashed potatoes. My son called home in tears pleading with us to not make him eat them.
My husband is king of mashed potatoes. My kids had never had the fake ones.
On the other hand, as a kid, I ate Potato Bud fake mashed potatoes all the time. I liked them and they were easy to make.