7_Ameyuri Ringo_7
NEEDS MOAR GYOZAS
Anti-zombie techniques are too advanced for ninjas. Look at Hidan. Asuma wouldn't be dead if he only knew to destroy the brain.
More serious answer: They seem to be taught to aim for the chakra center -- the heart. Kakashi has always aimed for the center of the chest whenever he uses his Raikiri. Haku, Kakuzu, even Rin were Raikiri-punched in the heart. I suppose that's the most conventional way to kill a normal ninja in the world of
Naruto.
Now that I think of it, I believe ninja logic is that forehead protectors are magical things that prevent people's heads from getting impaled, blown up, or magically imploded. AIM FOR EVERYTHING BUT THE HEAD BECAUSE THOSE FOREHEAD PROTECTORS WILL DO WHAT THEY WERE DESIGNED FOR.
(But they cut Hidan's head off instead of going for the heart. Couldn't they do that to Kakuzu? Or aim for the back of his head...)
Maybe Kakashi was always taught to stab people in the heart and Asuma (and Shikamaru by proxy) were taught to chop off people's heads. I don't know. It's grown up logic! They know what they're doing!
But yeah, it's not exactly a plothole but rather just bad tactics. You're dealing with two immortals. Sure it makes sense to do the decapitate and separate for one because he's a zombie but why treat Kakuzu like a video game boss where you
attack the weak point for MASSIVE damage?
Kakashi is a genius!