He's publicly aligned himself with KOT.D. Which came first, as in whether or not he aligned himself with KOTD and then stopped getting booked on Smack, or stopped getting booked first and then jumped ship to KOTD - I don't know enough about the situation to say.
He's also not a huge draw. I know he's an OG and gets respect, but I don't think any fans go out of there way to see him battle live. You can have the exact same card with or without him and attendance would be the same.