Why is this the answer?

The answer is riddle because this very clever puzzle is actually describing itself and how it works to challenge your brain! This is a special type of riddle that makes you think about the whole idea of a mystery question. Let us break down the clues, one by one, to see how they fit perfectly. The first line says, "I am never quite what I appear to be. Straight-forward I seem, but it's only skin deep." Think about a riddle you read. It usually looks like a simple poem or a short question. That is the "straight-forward" look. But the words are tricky! They mean something different than what they seem at first, which is why you have to look beyond the "skin deep" surface to the real meaning. A riddle is never just what it seems. The next clue explains the secret: "For mystery most often lies beneath my simple speech." A riddle uses easy, everyday words to talk about a common object, but it hides the object's name. For example, a simple sentence like, "I have an eye but cannot see," is really a clever clue for a needle. The mystery is the hidden object you are trying to guess. The last part of the riddle is the biggest hint of all because it tells you exactly what to do to solve a puzzle like this: "Sharpen your wits, open your eyes, look beyond my exteriors, read me backwards, forwards, upside down. Think and answer the question…" A true riddle forces you to "sharpen your wits" by thinking hard and looking for clues in every direction, even "backwards" or "upside down," until you find the solution. The whole poem is simply giving you the instruction manual for solving a riddle. Because the whole message is about the rules and secret life of a mystery question, the only answer that makes sense is the word riddle itself. It is a wonderful example of a word game that is smart and playful at the same time.