Because so much music has already been heard it doesn't require more listening to, right?
So one would think, judging from the right-note/wrong-note mentality so pervasive in the music pedagogy business. What is worth listening to is the child playing as well as the music being played.
I was recalling yesterday listening to one of the first LPs I ever owned, a recording of Arthur Grumiaux and Clara Haskell playing Mozart sonatas. As I listened the first time I was as if in heaven. The second time, some days later, was the opposite experience. I had already heard this! I had, essentially, memorized those wonderful sounds. Hearing them again somehow negated their power.
I could see the enemy in full view.
Think about it: Don't you recall specific sounds that you heard last year--maybe even five, ten, thirty years ago? Granted they have been distorted by many factors in the meantime, but don't they remain essentially as they were, precious because fleeting, once-in-a-lifetime events?