We have to consider that injuries will happen too. It's fine and even desirable to have our young rookies see if they can make it as a #6 D but if they can't, or if they can but there's an injury higher up on the depth chart, we need insurance.
Guys like Brisebois, and Sautner have a little more NHL experience but for Rafferty, Juolevi, Rathbone, and Chatfeld, it'd be dicey to have 2 or 3 of them in the line up at the same time at this stage of their careers