One possible reason could be his past traumas. Naruto grew up alone and was often shunned by the villagers. Physical touch might remind him of the times when he was pushed away or bullied, so he has developed an aversion to it in fanfiction.
It could also be related to his ninja training. He is always on guard and being touched might disrupt his focus or make him feel vulnerable in a dangerous ninja world. He has to be constantly aware of his surroundings, and unexpected touch could be seen as a threat to his safety.
Maybe Naruto just sees Sakura as a friend. He might have a different idea of his ideal partner and Sakura doesn't fit that. His feelings for her could be purely platonic.
Well, in some fanfictions, it might be because the writer wants to create an alternative storyline. Maybe they think Naruto has a different type of relationship in mind, like a more platonic or brother - sister - like bond with Hinata instead of a romantic one.
Maybe in some fanfictions, the writer portrays Kakashi in a way that Naruto doesn't resonate with. For example, if Kakashi is written to be too strict or distant in a different way than in the original story, Naruto might not like that version of him.
One aspect could be that it might explore a Naruto who is in a state of being 'untouchable' in a metaphorical sense. Maybe he has some sort of power or status that makes him unapproachable. For example, it could be a story where he is so powerful that other characters are in awe and can't physically or emotionally reach him.
Maybe they don't like fanfiction in general. It could be that they prefer the official, canon Naruto story. Fanfiction can vary greatly in quality, and they might have had bad experiences with some poorly written Naruto fanfictions in the past, which made them dislike the whole concept of Naruto fanfiction.
They can simply respect each other's preferences. The OC can choose to avoid fanfiction discussions and events while the enthusiasts can respect the OC's stance. For instance, in a Naruto - themed community, they can have separate areas or topics for those who like fanfiction and those who don't.
Well, there could be various reasons. Maybe the writer wants to create a unique situation where Naruto is silent to add mystery. For example, if the fanfiction is set in a scenario where Naruto has lost his voice due to a curse or some kind of magic. It could also be that the author is focusing on other characters' reactions to Naruto's silence, which can bring out different aspects of their personalities.
Obviously Naruto himself. Then there could be his friends like Sasuke and Sakura. Since Naruto is in this 'untouchable' state, they might be the ones trying to figure out what's going on and how to reach him again. They have a deep connection with Naruto, so they would be likely characters in the story.