Allegories and symbols speak to the unconscious. There can be many layers of meaning woven into them, because of the fact that they're not literal. This can also be a form of cryptography that keeps information hidden from those who should not have it or who are not ready. When you truly open your eyes, you will see things hidden in plain sight.
I've found the deepest meanings to be those that are sensed, those that stir the waters within. You don't get this if you process everything literally like a robot.