Because of Sasuke's attitude. If he was more like Itachi, he would've been a much better character.
Itachi wasn't perfect and clearly at the end of the story had a massive form of regret in his heart because of what he did in the Uchiha massacre. Itachi became a tool, acting like he loved the village even though the village never did anything to warrant such devotion and loyalty, his character is full of massive plot holes that could easily be avoided.
Sasuke was better than his peers in his time as a ninja in Konoha, and when he left I believe it was Naruto that decided to initiate their fight. When he went to the Five Kage Summit, he was attacked first, and then the Five Kage stopped him from chasing after Danzo but then blamed him for Danzo's escape.
On the Samurai Bridge, Sakura tried to kill him and he saw through it and tried to kill her first which failed. Then Kakashi tried to kill him which also failed, then Sakura tried to kill him again which also failed.
Sasuke is a character who makes decisions on his own, blunders, and makes mistakes in comparison to Naruto's ever perfect persona. Naruto fans seem a little jealous that Naruto has little to no intellectual or philosophical substance to him, and never changes throughout the story as things change around him. Arrogance is a flaw that all people with talent have, especially Itachi who admitted his arrogance when fighting Kabuto.
I was a Naruto fan but got annoyed as his character ignored Obito's words, and information like the Uchiha massacre. When Pain questions him about peace, he has no answer but idealistic dribble. His character's claim to fame is a borrowed power while Sasuke's abilities are his own besides Amaterasu. Sooner or later you'll feel disappointed in Naruto as a character.