I don't get it to be honest.
Nothing against Pat because he is a nice guy and a great musician, but he has absolutely NO stage presence playing guitar. He just stands there looking bored out of his mind.
I just don't get why he'd give up his drumming spot to some drummer for hire, just to stand there in the background and look totally bored and uninterested.
I guess it's possible he enjoys it, but it sure doesn't look like it.