You probably noticed that each time you were looking for a transcription of one of your favorite Oscar Peterson, you didn't find it. You can find different volumes, but none of them includes great pieces of Oscar. If you search for a McCoy Tyner it's even worse : almost nothing exists. About Art Tatum, he's probably the more transcribed, and we can buy a lot of great pieces.
But, most of the time, these pieces are unreadable. Often, the musical notation is not well observed, mixing sharps and flats in a silly manner that reveals a deep misunderstanging of what is a 'tonality'.
(for example, a C7 includes a B flat (7th) because we're in F. Not a A sharp. )
Even if you're good for reading, you'll stop on every chord, not finding the chord structures you're used to (stacked thirds...). As though Tatum was not difficult enough. As a result most of the time you give up, and close up the book.
We dont play Jazz on score, but I'm deeply convinced that scores dont hurt.
Even if Jazz is improvised, it uses a specific language (several in fact : blues, stride, bop, pentatonic, modal...) that must be studied and learned, or what you'll play wont be Jazz.
Jazzmen dont write their music... so I do !
These are my transcriptions.