The most beautiful piano music is hardly ever performed... because it is originally improvised music.
As it is created on the spot, improvised music has a spontaneous flair that "composed" music cannot match. When done by a grandmaster such as Keith Jarrett, and when everything falls into place, the result can be pure musical magic.
The primary source of improvised music is not a score, but a single recording. Therefore, to perform it again, one needs a brave soul that painstakingly crafts a transcription.