Perhaps he feels overshadowed within the Bat Family. Tim Drake is a smart and capable character, but if he constantly feels like he's in the shadow of Batman or the other more well - known members, he might decide to leave to prove himself independently. Fanfiction often explores these kinds of in - depth character motivations.
It could be due to a personal betrayal. For example, if he discovers that another member of the Bat Family has been hiding something important from him that makes him feel he can't trust them anymore. This would make him want to leave and create his own identity away from the family. In fanfiction, this kind of emotional turmoil can drive the story forward.
In some fanfictions, it could be due to personal growth. Tim Drake might have outgrown the role of Robin or the shadow of Batman. He may want to explore his own identity and capabilities independently, away from the Bat - family. He could feel that staying with Batman is holding him back from reaching his full potential as a hero.
The other young members like Robin (if there's a new one) or Batgirl could be affected in terms of their own development. They might start to wonder if they should also consider leaving at some point. And it could create a sense of instability within the group as they have to adjust to not having Tim around.
One possible reason could be that he feels misunderstood by his family or friends. Maybe he has some secrets that he's afraid to share, and the fear of being judged makes him run away.
His relationship with the Bat - family would likely be more strained. Since he was raised by a dragon, he might have different values and ways of doing things. For example, he could be more impulsive like a dragon in combat rather than following Batman's strict rules. This would cause friction with Batman and the other Robins who are used to a more controlled approach.
Perhaps Naruto has some unresolved issues from his past that he doesn't want to burden his family with. He may think that leaving is the best way to deal with these issues on his own, without putting his family in the middle of his personal turmoil. He might go off on a solo adventure to find himself and come to terms with his inner demons.
The plot could shift focus completely. Maybe the fanfic was about Tim Drake's relationships in Gotham, but once he leaves, it could turn into a story about how Gotham changes without him. It might explore how the villains react to his absence or how the city copes without his vigilante presence.
In some fanfictions, Harry might leave his family because of a prophecy or a special mission. He might feel that he has to go it alone in order to fulfill this prophecy or complete the mission successfully. His family might not understand or be able to support him in this, so he decides to leave. Also, there could be jealousy or resentment within the family that makes the environment unbearable for Harry.
One great storyline could be them teaming up to solve a mystery in Gotham that the Bat - family has overlooked. Maybe a series of strange disappearances that seem to have no connection at first, but as they dig deeper, they discover it's all part of a grand scheme by a new villain. They would use their unique skills, Bat Girl's martial arts and detective skills, and Tim Drake's brilliant mind and acrobatic abilities to piece together the clues.
Well, he might receive a mysterious gift that leads him on an adventure. Maybe it's a clue to a long - forgotten case. So he starts following the trail, which takes him all around Gotham. Along the way, he runs into some of Gotham's rogues who are also intrigued by the mystery gift. But in the end, he figures it out and it turns out to be a really special present from Bruce Wayne, like a piece of his father's old detective work.
One reason could be that the writer wants to explore new storylines without his character. Maybe they feel his arc has reached a natural conclusion in their fanfic universe. For example, if the story has been centered around Tim Drake's detective work for a long time, the writer might decide to shift the focus to other characters by having him leave.