Pure speculation, but does this impose an upper limit on the complexity of music you can play? Personally I cannot fathom someone play Liszt complete my by ear.
I took piano lessons for years, but was never good at reading music. I excelled at playing by ear. But when I wanted to learn something truly technical and challenging, there's no way I could have done it without sheet music.
Case in point: Imagine trying to learn this [0] by ear.
