The problem is time. Getting 140+ people to learn their instruments is hard enough, mixing in Music theory is just gonna add to the frustration, for which most of the band will never need to know.
That even holds true for everything but the smallest of jazz combos. Could you imagine listening to a group of 20 musicians all playing from Fake Books? It would be a mess of noise.
> for which most of the band will never need to know.
What do you mean by "need"? I think, for the purpose of playing music, music theory is more useful than reading. But no one really needs to do music in the first place. It's recreation and fun and expression.
20 musicians can work together. They'd need to know how to listen and make space.
That even holds true for everything but the smallest of jazz combos. Could you imagine listening to a group of 20 musicians all playing from Fake Books? It would be a mess of noise.