The When is December 31, 2016. That New Year's Eve show at Knuckleheads was officially his last gig.
The Why isn't 100% clear. Last I talked to him, he was still friendly with the band. He hinted in an interview at one point that he preferred the Power Trio format and didn't like the direction she was going in with the bigger band. he was playing with Paul Nelson for a while, I'm not positive if he's still with Paul.