Paul Heyman on WWE Creative Team

Why did Paul Heyman leave the WWE Creative Team?  His work for the Smackdown Brand in the early 2000's got a lot of praise.  With them bringing back Bruce Pritchard and Jeff Jarrett to be a part of creative recently, I wonder why they never asked Heyman?  (Or in fact they did, and he turned them down?)

It was mostly a personality clash with Stephanie that was only going to end one way.  Even now, lots of people don't like him, so I can't imagine wanting to have him around the writer's room or him wanting to be there.