Maybe he just feels it doesn´t need it. Or maybe now that he´s connected to the Juubi by those things he´d end up using its chakra for the Susano'o at which result I´m unsure it´d turn out, but Obito said he´d prefer conserving as much of its power as possible. Oh wait, he´s not connected anymore.....mah whatever. It doesn´t look like it´s taken a beating from anything other than the stunt Bee and Gyuki pulled with the Tailed Beast Bomb down the throat.
But now that he´s not connected to it he might as well use his own infinite reserves for his Final Stabilized form (or Perfect Susano'o as you guys call it) against the Alliance Forces to counter their collective power-up.