Especially (God forbid) if we need a new CJ before the Court leaves for the summer. We don't need a double knock-down drag-out when there's cases that need to be heard.
What happens when a Justice leaves before cases are decided? Can a new Justice who wasn't around during oral arguments have a say on a decision? Or will we be stuck with a bunch of 4-4 decisions?
Personally I think an even number of justices would be a good way to keep them from causing trouble which mostly comes from the 5-4 decisions. Of course I wouldn't want that with the four nuts we have there now!