11. "To extend the thought, it's worth thinking about the..." In response to In response to 9
...relationship between repetition and commercial appeal.
Generally speaking, the degree to which jazz is improvised is inversely proportional to its mass popularity. Improvisation is by definition unpredictable (or should be, given a competent soloist), and unpredictably isn't what the masses want. You can't hum along to a 12-minute extemporaneous exploration of all possible modes of F#, but you surely can with jazz that features strictly composed, regularly repeating patterns and recognizable structures.
Swing featured the latter, and was danceable to boot. You mentioned Weather Report...those guys played arenas in the late '70s, because Birdland et al. are essentially pop songs.
On the other hand, variant like hard bop and free jazz are loved only by aficionados, with a few exceptions.