Rok, you and Frogman are making interesting conversation, but you both are totally wrong.
Do you recall an interview with Herby Hancock, where he stated how he goofed (played wrong chord or notes) and Miles came right behind him and made it all perfect; Miles thought that was what Herby intended to play. Improvisation is spontaneous, there is nothing predetermined about it.
Evidently, what you and Frogman can not comprehend, you must find other reasons for it's existence; I have seen jazz musicians perform impossible feats night after night; they're jazz musicians, that's what they do.
No matter how many people the concert pianist reached, the music was right in front of him and it may have been hundreds of years old; "external", outside of one's body; "internal", from the soul, that inner spirit that makes us alive, and different from every other human being on the planet; that's where the jazz musician is coming from.
In regard to reaching people, I'm sure the concert pianist reaches his desired audience. I may not hear anything when I look at a Beethoven piano sonata, but a concert pianist most certainly would when he looked at it; but did he create it?
Building blocks, nuts and bolts; I assume you are referring to the stuff that makes music; if so, all musicians use the same nuts and bolts, they just arrange them differently.