In case you've never heard the term before, skeuomorphism in design is a visual holdover of the familiar. It is why your camera app looks like an old camera; why the your phone's calendar looks like a wall calendar, etc. These visual cues usually tell the user what to do with an item that is completely out of its normal context. Once the user is familiar with that behavior, though, the skeuomorphism holds no purpose. Here are 4 reasons why these visual references will actually hurt your UX instead of help it.
Burdening your designs with user assumptions
Want to make a layout intuitive? Skip the skeuomorphism and stick to basic design principles like hierarchy and the grid. Making your reading app look like a bookshelf will communicate that your user should "pick up a book" - but that's about it. Any cool chat function you build in might go undiscovered as it is not automatically related to a shelf and not obvious.
Wood paneling, stitched leather and binder rings will make your UI look completely out of date in the age of iOS7. Understand the needs and sophistication of your users and cater to them without all of the space-wasting frills.
Limitations in functionality.
In the real world, 3D objects usually serve a single main purpose. You wouldn't expect your bike to also make your coffee in the morning (not yet anyway!) and you wouldn't expect your kitchen chair to have Netflix installed. In this same vein, trapping your UI in skeuomorphism and real world references will limit your creativity. A forward thinking notes app should absolutely handle your larger time management needs, but it won't engage your audience if it looks and functions like a clunky trapper keeper.
Your users will see you as lazy.
In a world of digital possibilities, the choice to reference the real world leaves many users bored. Why not rethink how they should interact and better manage the information you are presenting? The more thoughtful and effortless you make the UX, the more your users will come back for more and ultimately advocate on your behalf.