Another reason could be for disguise. Naruto might be in a situation where he needs to hide his identity. By covering his eyes, which are a very recognizable feature of his, he can make it more difficult for others to figure out who he is. This could be especially important if he is in enemy territory or trying to infiltrate a group secretly.
One reason could be to explore the darker side of the Naruto universe. Writers might want to see how the characters and the world would react to such a major loss.
Power imbalance could also be a reason. If Naruto's power suddenly goes out of control or he misjudges the Teen Titans' power levels and thinks they are a danger to his world or friends, he might take extreme actions. For example, if there's some kind of power - up in Naruto that makes him overly confident or paranoid, he could lash out at the Teen Titans thinking he's protecting something important.
One possible reason could be that the council has been secretly plotting against Naruto all along, perhaps trying to undermine his power or even get him exiled. Naruto might have discovered their malicious plans and decided to take pre - emptive action to protect himself and his friends.
It could also be due to a misunderstanding. In the heat of the moment during the vote, there might have been miscommunications or false assumptions. Naruto might have thought Sasuke was going to betray them all and in his haste to prevent that, made the tragic decision to kill him.
One reason could be that Naruto has always been more attracted to those who understand his outcast past better. Sakura doesn't really have that kind of connection with him as she comes from a more normal background. So there's a lack of that fundamental understanding between them which hinders any romantic feelings.
One possible reason could be a miscommunication between them. Maybe Anko feels neglected and then strays. Another reason might be that the writer wants to create a more complex and angsty plot.
Perhaps he's trying to protect himself from some kind of danger. There could be an enemy who is looking for him and by covering his face, he can avoid being detected easily. It could also be a part of a new jutsu or power he has discovered where covering his face is necessary for its activation or control.
One possible reason could be for Naruto's protection. His father might think that by locking him away, he can keep Naruto safe from the many threats in the Naruto world, like powerful enemies who might target Naruto for his special powers.
One possible reason could be a sign of extreme loyalty and friendship. Naruto might see Yang in a dire situation where she needs his arm for some crucial purpose, like to complete a powerful jutsu or to defend against an overwhelming enemy. He is known for his selfless nature, so sacrificing his arm would be in line with his character.
One reason is that some fanfiction authors may lack a deep understanding of Naruto's character. They might write things that are completely contrary to his values and personality just for the sake of creating a 'unique' story. For example, Naruto is known for his positive attitude and strong will, but in some fanfictions, he could be depicted as a negative or spineless character.