I think Madara isn`t using because he want`s see how far will go Obito and maybe he can`t right now, because he needs a lot of concentrate for control Juubi. I don`t remember which chapter, but Obito stated when he was conroling jincuricens, he need concentrate to controling or he loses control.
reread manga i find something interesting. where Itachi and Sasuke fight there on wall was Eddy clans symbol in capter 385 page 7 and 15.. but maybe I`m wrong.