Yes, I have heard lots of jazz; although I can't provide you with the ticket stubs and receipts for every show I've been to (which means I haven't ever been to any, right?) Everyone on my wifes side of the family plays in various groups in and around the New Orleans and Baton Rouge area. Ones a drummer, ones a sax and piano player, ones a bassist (hes probably lurking around here somewhere.) Every time I talk to them, or go to the area, they have me go watch on one of their shows, or one of their friends shows. They constantly try to convince me that jazz is entertaining. Jazz entertains me about as much as a Ziggy comic entertains a door hinge.
Every time this discussion comes up people try to introduce me to more jazz, or better jazz, or the right jazz, or educate me on how great jazz is in some other fashion. Over and over again, like the 15 year old who thinks he is the first person to ever discover Frank Zappa and tries to convince you that Zappa is the greatest musician of all time past and time to come.
So far there have been two major points made in this thread.
Horns: I hate horns. I have never heard a solo horn player perform at a reasonable volume for the situation they are in. Although acceptable in supportive groups of three or more, any of the hundreds of different solo horn players Ive listened to seem to feel the need to seek vengeance on the ears of everyone around for being the only guy having to regulate their breathing patterns. The horn players give the entire jazz community a bad name. If I see a marquee for a jazz band that features the sultry dynamic sounds of John Tromboner, I cringe and keep walking; instead of not cringing.
Accessibility: Other than the rare instance where a jazz crew employs the labor of a hype man, or just has exceptional stage presence, jazz is boring. That is why people want it as a background sound to what is going on; jazz by itself holds peoples attention for a shorter time than a gold fish remembers what youve named it. The band playing jazz could be just as happy playing to a crowded coliseum as they could playing on the back porch, the audience doesnt matter. It is not for an audience, it is for the musicians. Unless the audience is made up of musicians and they are actively studying the musical event unfolding before them. It is a practice of study. If you arent watching a jazz team and studying what it is that they, or any individual playing, is doing as, as a musician, then you are probably more worried about how large your bar tab is than the music.
And my point of lacking spirit: Someone else up there in the above comments said something about jazz being like watching a bunch of dudes solve math problems. That is a great way to state the lack of spirit, and also ties into my argument for accessibility. The music is great for the performers, but to sit there and watch a guy noodle around until he finds the one again and call it avant guard talent is crap. Listening to a drummer, a bass player, and either a pianist or guitar player all playing together; then having another one or two guys go off on their own thing is annoying. It always reminds me of when you are at band practice and trying to work out a part with the new guy, while one of the other guys not paying attention to what is going on starts wailing away on his tool of destruction and distracting the entire room from the task at hand.