Thinking more about textures and skeuomorphism, another point occurs to me about textures in iOS.
What purpose does the “Corinthian leather” serve in a Chrysler? What purpose does green felt and wood serve in a casino? These surfaces could be covered with materials of different color and different texture. They could be covered in materials with a flat texture and painted in flat colors. These textures are just as superfluous—or purposeful—as they are in the digital world as in the real world.
You may not like the specific choices in either the real so digital world, but the aesthetic choice is just as valid in either case.