They probably get a bug or two in the frosting every now and then, but I really don’t think it is that big of a deal. Think about if you were outside eating a sandwich. You’re not going to have an infestation of gnats immediately drawn to your treat. It doesn’t work that way. Bakers and cake decorators just move as fast as they can to get the cake inside, but if there is a stray bug that lands on it, I’m sure it’s an easy fix.