From Listen magazine, an excellent article on the creative surge happening in the wind band world: Beyond the Halftime Show: The American wind ensemble is quietly building a canon.
As the article quotes John Corigliano:
The repertoire of band music is largely contemporary. As a result, the audiences expect and look forward to new works. Listening in an environment largely ignored by the press, they learn to trust their own ears and respond directly to what they hear. Most important of all, concert bands devote large amounts of rehearsal time over a period of weeks — not days — to learning thoroughly the most challenging of scores.
So the appeal to composers is obvious. If the medium continues to be more and more appealing to composers, well...where the composers go, so goes the musical culture.
(You can download Corigliano's absolutely fantastic symphony for band, Circus Maximus, here. And it's only eight bucks.)