Agreed, but reading sheet music is a very small part of playing piano proficiently (say, at the 97th percentile). Once you get past knowing the notes in a piece, there's the much more difficult task of being able to manipulate the force that you exert from your fingers to create the right volume balance. For example, your untrained thumb will naturally play notes much louder than it should, and it takes a lot of practice to be able to play notes with it at the right volume; the opposite is true with your pinky and ring fingers.

...Not to mention the even more difficult task of knowing what you want the piece to sound like in the first place. A novice playing a piece at 100% accuracy sounds nothing like a concert pianist playing the piece. There's a world of depth to music beyond just learning the right notes.

Here's an example: listen to this performance of Debussy's "Reflets dans l'eau" by Arturo Michelangeli, one of the greatest pianists of the 20th century:

https://www.youtube.com/watch?v=LLbpQl1cCl8

And then listen to this student play it (she is still a high-skill player, just not world-class talent):

https://youtu.be/l2gJSVOdaG8