Reading music is a great AID to learning tunes but I have found a tendency among players who learn from the dots that if you take their dots away they're struck dumb, even if they know the tune. Relying on the dots can be a hindrance too.

Also ,if you find yourself humming a new tune you have thought of, how are you going to record it for posterity. Using the dots can be more than useful then. There's two sides to every argument.