I have wondered the same thing.  Maybe he's disfigured.  Maybe he has a lazy eye.  Maybe he just thinks he is a rock star! 

Well, I know that the first two are wrong, because I have seen him without those great shades, so there has to be some other reason.  I decided to do some research and found an interview where he was asked just that same question.

Click here to watch!

Now if you are wondering just what those cool shades are, we found that out as well.  They are RB3025 Aviators.  Looks like a silver frame and just dark lenses!  You could look like Eric when you perform too!