Someone at mudcat in the songwriting thread said this:
One of my old band mates liked to point out that an audience will like a bad band that plays material they know better than a great band playing material they don't know—

I think that explains it. Same reason Hollywood does remakes/sequels. It's proven over and over again that there is more money in the familiar than in the new.

I don't think we're suffering from a lack of creativity, there are plenty of creative folks around, it's just that the paying public or club owners don't want it. It's the dumbing down of the arts. And a catch 22. People only want what they already know so how do you get them interested in something new? Very sad!