One possible reason could be that they are too involved in their own shinobi duties. The world of ninjas is full of dangerous missions, and they might be constantly away on important tasks, leaving Naruto feeling neglected.
In this fanfiction, it could be that Naruto's parents have some sort of prophecy or important mission related to the entire ninja world. They believe that their focus on this larger task is more important than being there for Naruto on a daily basis. Another reason might be that they are part of some sort of political intrigue within the village, and they have to be very careful about their actions, which unfortunately leads to Naruto being neglected as they are too distracted by these complex matters.
Naruto might try to seek attention elsewhere. He could focus on his training more intently. By pouring his energy into becoming stronger, he distracts himself from the pain of parental neglect. Also, his friends could play a crucial role. Their friendship might give him the sense of family and belonging that he lacks at home.
One reason could be that his siblings have some special abilities or talents that overshadow Naruto. In the ninja world, those with unique powers often get more attention. So, if his siblings possess something extraordinary, Naruto might be pushed to the side.
He might have a stronger sense of justice. Because he has been through so much pain and neglect, he doesn't want others to suffer the same. So he is more likely to stand up for the weak and fight against injustice. He has a deep - seated understanding of what it's like to be alone and picked on, and this fuels his desire to create a better world for everyone, especially those who are also neglected or oppressed.
Maybe there are secrets in the family. For example, his parents might be involved in some dangerous and secretive missions that require them to keep their distance from Naruto to protect him, but Naruto misinterprets it as neglect.
Maybe he's been influenced by someone who has a different view of heritage. For example, if he meets a character who believes that one should create their own identity rather than relying on heritage, Naruto could be swayed. Another possibility is that he has some sort of resentment towards his heritage. Perhaps there are things in his family's past or in the traditions associated with his heritage that he doesn't agree with or is ashamed of.
It could also be due to some family curse or prophecy. In the Naruto universe, there are often strange powers and curses. Maybe there was a prophecy that said Naruto's family had to keep their distance from him to protect him from some greater evil. So, they chose to neglect him in order to keep him safe, even if it was a difficult choice.
In this fanfiction, it could be that Naruto's parents were under some sort of mind - control. Some evil entity could have taken over their minds and made them feel hatred towards Naruto. Also, it might be related to a family secret or feud. There could be something in the family's past that made them believe Naruto was a stain on their family name, even though Naruto himself was innocent. It could also be a case of false information being spread around the village which made his parents believe lies about him.
One possible reason could be that they are too focused on their own problems or duties. Maybe they are involved in some important shinobi business that takes up all their time and attention, causing them to overlook Naruto.
In this type of fanfiction, Naruto could have a different attitude towards authority. As his parents are neglecting him, he might not have that natural respect for figures of power. He may question the village's system more. Also, his dreams of becoming Hokage could take on a new meaning. Instead of just seeking recognition, it could be a way for him to create a family - a village where no one is neglected like he was by his parents.
It could be that in this fanfiction, there are some external influences like an enemy who has manipulated Naruto's mind. The enemy might have planted false memories or ideas in Naruto's head, making him believe that his parents are not who he thought they were, leading to his rejection.