Each one costs something like 300 grand. Sure, it's a drop in the bucket for NBA teams, but it's still money and if they get no time, it's wasted. besides, we'll need room on the roster to pick up salary for players and draft picks. Guess we could drop them before their contracts go guaranteed, but again, why?
The only way I see this is if Rush/Kanter aren't ready at the start of camp. (aka CJ having a busted wrist and finding Matthews)