Because Pop-Tarts and Skittles aren't being sold as a food replacement. I don't know about you, but I'm going to hold someone making a "snack" to a much lower standard than someone selling a product marketed with, "Here, you can use this instead of eating."
Yeah, that's sort of true... but I think people do see these snacks as real food. Pop-tarts are marketed as a breakfast food - this makes it seem as though you could eat pop-tarts in the morning before you start your day instead of a fruit salad or something more "time-tested"
