Joe won’t be making the actual decision, so why the delay?
The Hillary and Obama camps can’t settle on a price? Or a mutually acceptable candidate.
Or they are too busy threatening each other with what they will do to each other (or to the Biden camp) should the other get their way.
Or the two camps can’t come to a deal whereby Biden is offed and one person from each camp gets one of the slots—but which one gets which? Therein lies the rub.