Yeah, I think it comes down to not all the songs having keys on them. Also as someone already said, alot of the piano and keyboard parts were played by Axl on the albums anyway. And with the Spaghetti Incident?, being a punk rock tribute, Dizzy wasn't going to feature heavily on there anyway. But live Dizzy does add keyboards to guitar driven songs, and I must say he does a great job and it sounds awesome.