What could be the reasons if Snape gives up fanfiction?

It could also be due to some external factors. Maybe there are threats from dark forces that he doesn't want to involve Lily in. If he is getting deeper into the dark arts or some dangerous situations, he might choose to give up on her to protect her from the potential harm that could come her way because of his associations.

It could also be that he is tired of the false expectations created by fanfiction. In fanfiction, his character might be portrayed in ways that don't match who he really is. He wants to be true to himself and his ninja way, so he gives up fanfiction.

One possible reason could be a lack of time. Maybe Ash has become too busy with other aspects of life, like work or studies, and can't find the time to write fanfiction anymore.

One possible reason could be that Izuku realizes Bakugou's unchanging and hostile attitude. Despite his efforts to be friends or get along, if Bakugou continuously rejects him or is overly aggressive, Izuku might feel it's a lost cause.

One possible reason could be that she loses inspiration. Maybe she has explored all the ideas she initially had for her fanfiction and can't come up with new and exciting storylines. Another reason might be lack of time. If she gets involved in more important or urgent matters in the RWBY universe, she simply doesn't have the hours to sit down and write fanfiction anymore. Also, she could face criticism from others which makes her lose confidence in her writing and decide to give it up.

One possible reason could be that J.K. Rowling, the author of Harry Potter, has strict control over the franchise and might have made some regulations that made it difficult for him to continue. Another reason could be that he simply lost interest in writing fanfiction about it. Maybe he wanted to focus on creating his own original stories instead.

It could be that in this fanfiction, Ash had some personal issues come up. For example, he might have received some bad news from his family back home that made him lose focus on training and eventually give it up. Another reason could be that he found a new passion or interest that diverted his attention away from training.

One possible reason could be that Ginny realizes Harry is too preoccupied with his heroic duties and she feels neglected. In fanfiction, this is a common trope where the female character desires more attention in a relationship.

Maybe Stiles has been constantly disappointed by Derek's actions or lack of response in the fanfiction. It could be that Derek has repeatedly let Stiles down, and over time, Stiles just can't take it anymore.

One reason could be repeated heartbreaks. If she has been through multiple bad relationships with men in the fanfiction, it would lead her to give up. Maybe she constantly faced betrayal or being taken for granted.