Jazz's contemporary convention is a result of the recording industry. Recordings are a mixed blessing. Having been a commercial boon to players and their distant fans, recordings are also a deceptive tool for learning. They are artefacts after the fact. Jazz is a process of adjusting to the musical moment.
Listeners get a frozen moment's dressing up of a piece of music.
They hear it over and over. It becomes fixed in their minds. What really matters, the process that fleshes-out and gives life to the skeleton, is often forgotten, if even recognized. A skilled jazz improvisator will not know or plan entirely in advance what he or she is going to play. A player's input, in turn, will cause other players to respond, and so on.