Love how Madara blocks a Bijuu Bomb with it but Obito can't block a Rasengan with it.
I would assume that if it is a tool of SO6P, it requires an abundant amount of chakra to use, and Tobi was already using enough chakra as it is.....or perhaps he just didn't know how to wield it properly.
Who remembers the days when a weapon is a weapon, and not some doom device with hidden haxor powers? Need another example, look what kishi did with the swordsmen.