If [Demonic Statue of the Outer Path](http://naruto.wikia.com/wiki/Demonic_Statue_of_the_Outer_Path) requires only a part of the chakra of the Nine-tails and the Eight tails, why did they have to kill the other Jinchuuriki to obtain the tailed beast just to complete the Juubi? 

Why not obtain only parts of the chakra of each tailed beasts?