It's because he was planning on ending the manga then, Naruto "surpassed" his predecessors and finally became acknowledged by the citizens of the leaf for defeating the man who destroyed it, the final boss, the leader of Akatsuki which at that time was the end all be all badasses of the series, and Sasuke got revenge on a man he spent the entire series till that point promising to kill, and did so against someone with the best attack and defense ever, without "doing it his way" by which I mean obtaining a Mangekyo. Theeeennn money was thrown in Kishi's face and that's why every moment since then has been really random and full of plot holes.
