I answered this somewhere before.
Sometimes artists are difficult in rehearsals and at the first couple of shows, then their nerves settle down, they chill out and the tour becomes a pleasure.
Also, I was their third option (after Jeff and Manu), where are you going to find a decent drummer at very short notice. You have to think about the other band members, the crew, the management. You don't want to drop everyone in it.
I agreed to do the tour and I honoured that agreement. In fact I worked very hard every show (like the rest of the band).