If you think about it a certain way, one of the defining qualities of jazz is earnestness. This is one of the reasons why jazz and metal have so much in common, and so often appeal to the same listeners. Both forms can be totally absurd. Think of the most lurid, squiggly fusion, or the blare of a thoroughly unsubtle big band record; aren't they the equivalent of, say, DragonForce? But metal's awareness of its own absurdity does not translate into ironic distance from what they're doing. And the same is true of jazz. People will play the most ridiculous, over-the-top shit with a totally straight face. Even when a jazz group exhibits a certain amount of wit — think of the Bad Plus in their original incarnation, the version that covered "Smells Like Teen Spirit"; or Mostly Other People Do The Killing, and the way their sleeve designs imitated famous jazz album covers — it's done out of love, not mockery.