Board Thread:Theories and Speculation/@comment-25139119-20150807165411/@comment-2120712-20150809000331

Maybe Naruto has to ask for the TB to give him their chakra in order to access that mode. That was one of the reasons why Hagoromo had Kurama go back into Naruto, to act as an living telephone pole/receiver so that the beasts have a medium to talk to each other over long distances. As for why Naruto didn't ask for said chakra, either plot induced stupidity so that the MV would not get one shoted by a Sage Art: Super Tailed Beast Rasenshuriken. Sasuke got his sage powers minus the hand mark back in the Gaiden, who knows if Naruto will get his back in some future media.