It's not just "plot no jutsu". Kishi has written his character that way because Sasuke was never intended to be the main villain, he was never intended to be as ruthless and totally heartless as someone like Orochimaru who just does things for the hell of it. Sasuke has always had reasons to do what he plans to do, but then something, whether it be someones words, more information gained, or his own mind/heart.. stops him from carrying out acts like killing his comrades.
Recent examples: Sakura. He had a huge opportunity to kill here right then and there. If he didn't care for her as at least a friend, he would have killed her.(if not as a friend then he knows that Naruto cares for her a lot.)
Kakashi. He is in a super weak state right now and also without sharingan, Sasuke could have put him in a simple genjutsu to shut him up, or killed him... but he didn't. He listened and even thought about love in general. Sasuke's brain is childlike still in terms of his understanding of love. He thinks of his family when it's mentioned, not romance.
So, it's not just plain old PNJ and that's all there is to it, it's something more when it comes to this character. I'm honestly not a Sasuke fan, I was in part 1 but that was before this place even existed.