why didn't ben best come back?

i know he was busy with music in the second season but he still came back for a couple episodes - why didn't he ever come back for the third or fourth? clegg was one of my favorite characters.

he didn't work at all on season three or four and had his credit removed, and hasn't worked on anything with mcbride or jody hill afterward - did they have some sort of falling out?

baby can you dig your man?
he's a righteous man.