Board Thread:Theories and Speculation/@comment-25093611-20160322113057/@comment-25122992-20160323222233

The main problem - Kakashi is not the true owner of these eyes (and only the true owners can handle these eyes with no problems) and he has neither Uzumaki's life force (as Nagato) nor Hashi's cells (as Obito, who even still had problems with it) to use it properly without exhausting immediately.