In Uglies, appearance is right where it should be: out in the open. A lot of this book involves people arguing over prettiness vs. ugliness in very open ways, as Tally and Shay do. "Appearance" in this book isn't just people saying "I like your hair"; it's more like, "I like your hair, therefore I want to be friends" or "I like your hair because it's like everyone else's and now society is equal." But by the end of the book, we're left wondering: if we're supposed to be learning that appearance doesn't matter, why does Tally end up undergoing the pretty surgery?
While David argues (after-school-special-style) that what's inside is important, the book shows how important appearances are.
Uglies doesn't talk about coming-of-age changes like puberty (your ugly, changing body) or other natural changes in order to focus on the unnatural pretty surgery.