As I was making red mashed potatoes with the skins on at Thanksgiving, a 7-year-old guest asked me why there were skins in. I replied that it was added fiber and vitamins, and also looked pretty. She countered with "No they're not - that's what lazy adults say so they don't have to peel them!"

Am I wrong? Are there really no added benefits to leaving the peels on like there are with other fruits/vegetables?