It doesn't, really. I don't mind if people post jazz pieces. I should have said "not necessarily jazz." My purpose in creating this thread was because throughout the years since I began endeavoring to learn to improvise, I've always been interested in music that sounds heroic, dark, urgent, passionate, intense etc. I went around the internet searching for people who did this sort of improv, but the only people I could find were improvisers of jazz elevator music, which did not interest me in the slightest. Bar music. You know the kind. That sort of improvisation has ten thousand self-help books and has been beaten into the ground. Eventually I made some friends, mostly on this website, who did improvisation which was not jazz, not classical, but something new entirely. Spontaneous, continuous creation of original music which was melodic and intriguing and had far more impetus than elevator music bar music jazz. This inspired me to do even more with my improv, and I continue to this day. I perceive there are few people who do improv with this sort of internal, obsessive drive to create original music, so that's why I created this thread.
In fact, I think I created the thread for "spontaneous composers" rather than improvisers. It was just my personal preference...if someone else wanted to create a thread devoted to jazz, more power to them.