im guessing cuz he cant use it?...cuz it takes too much chakra to use them as u can see in the manga and the only ones who can maintain a grip on the weapons are those with big amount of chakra...like jinchurikis ^^
i dont even play the video game X)) but since i search about that stuff it appears in a lot of videos...Besides its the only Video that explains the Senju and the Uchiha fight...am i not right? so its the only source of information...
http://www.youtube.com/watch?v=hs5KQLX3Prs