Go get yourself a comic book, or any other rectangle that measures roughly 10” on the diagonal. Hold it as though you’re reading what’s on the surface.
You see the problem? Your fingers get in the way. Think about how big that surface is, too. That’s a lot of acreage to scan, looking for the right buttons to push.
While you’ve got it in your hands, imagine that it’s a sheet of thin steel. That’s heavy, isn’t it? Hard to hold up for long periods of time.
Think about how a user interface would have to incorporate those observations. Now imagine that you’ve been doing this experiment for four years and not four minutes.
It seems to me the hardest thing about doing great industrial design is having sufficiently high standards and taking the time to meet those standards. Which honestly doesn't seem that hard. How come no one can compete with Apple?