Nothing short of that thing called plot. Couldn't Obito have just Kamui'd every Jinchuuriki one by one out of the villages and back to hideout for extraction? Plot strikes again!Couldn't zetsu have kidnapped naruto at the valley of the end? He was unconscious, and could easily get there before kakashi...
Remember they needed to seal the Kyubi last, therefore keeping him caged up and liable to release the Kyubi or do something that may harm the akatsuki was very high!Couldn't zetsu have kidnapped naruto at the valley of the end? He was unconscious, and could easily get there before kakashi...