J Ive manages and coaches a team of industrial designers and their collaboration with engineers. You cant be very effective, no matter how good you are, when you are on the other side of the world - someone would surely step up and take his place.

Also, Jobs has shaped Apple culture to put crucial importance on industrial design and is very hands on with the decisions. This influence coming from the top, serves Apple well no matter who is the VP of iD is... as long as Steve is around.