One possible reason could be that he's afraid of the power he discovers within himself. He might run away to avoid being corrupted by the dark side of the Force that he senses growing in him. It's a common theme in 'Star Wars' where characters struggle with the duality of the Force.
Luke could run away because he feels he has let down his friends or family. Maybe he made a mistake during a battle or a mission, and the guilt drives him to flee. He might think that by leaving, he can protect those he cares about from any further harm he might cause.
One reason could be that Vader represents the dark side which has brought so much destruction in the galaxy. Luke, being on the side of the Jedi and good, would naturally despise the evil deeds associated with Vader.
Luke runs away to a desolate planet. There, he tries to hide from the Empire and his own past. He lives in solitude, meditating on the Force and trying to come to terms with his inner turmoil. However, he soon realizes that he can't escape his destiny forever.
In certain fanfiction, Luke's actions might be misinterpreted, leading to the idea of him being a traitor. For example, if he discovers a long - hidden truth about the Jedi and the Sith that challenges the established order. His attempts to expose this truth could be seen as traitorous by those who want to maintain the status quo. He might also be forced into situations where he has to work with the 'enemy' to save his friends or the galaxy, and this cooperation is wrongly construed as betrayal.
There could be several reasons. Maybe he felt fanfiction misrepresented his character or the Jedi ideals he held dear. Fanfiction often takes creative liberties that might not align with how he envisioned the Star Wars universe.
Maybe he's running away from the pressure in the village. There are always high expectations on him, and he might feel suffocated and need some time alone to figure things out.
One reason could be to control him. Vader wants Luke on his side, and by locking him up, he can limit Luke's actions and try to influence his decisions.
There could be such a fanfiction. Fanfic writers like to explore different facets of their favorite characters. In the case of Luke from Star Wars, his not eating could be a plot device. Maybe he's on a dangerous mission and has no time to eat, or he's in a state of distress and has lost his appetite. This could lead to an exploration of his character, his relationships with other characters who might be concerned about his lack of eating, and how he overcomes whatever is causing him not to eat.
One possibility is that the Sith or some dark side cult would kidnap Luke. They'd want to either corrupt him or stop him from being a threat to their plans. Luke is a powerful Jedi, and getting him out of the picture would be a major advantage for the dark side.
It adds new perspectives. Fanfiction in general allows fans to explore different 'what - if' scenarios. In the case of Luke and Leia, it can make the characters more relatable by showing them in situations not seen in the official movies. For example, seeing them deal with everyday problems on a planet after the war is over.
In fanfiction, a 'spacer' Luke Skywalker could be on a mission to spread the teachings of the Jedi across the galaxy. He'd use his starship to journey to various systems, facing challenges from pirates or the remnants of the Empire. His experiences as a spacer would shape him into an even wiser and more powerful Jedi.