I blame my early music education. It was reading only and Classically oriented. My ear training was terrible well into College. I now use my IPAD for Lead sheets. I've learned to improvise on my own but just don't have that photograpic memory some musicians have.
I did some research a while back for the manager of a music store who didn't believe some of the top entertainers use monitors. Imagine doing the same songs your famous fo at endless shows and still needing a helper "just in case" Makes me feel OK as I don't do the same songs over and over .