There could be many reasons. One is that some fans may not like the way the original story portrays Sakura's love for Sasuke as being one - sided for a long time. By writing fanfiction where she doesn't love him, they can rewrite her story to make her a stronger and more self - reliant character. Also, it might be a way to introduce new plotlines and interactions with other characters in the Naruto universe that were not possible in the original story due to Sakura's preoccupation with Sasuke.
Well, perhaps the writers feel that the Sasuke - Sakura relationship in the original was a bit forced. So they create fanfiction where Sakura doesn't love Sasuke to explore different relationship dynamics and character arcs for Sakura. For example, she could have a more platonic or even antagonistic relationship with Sasuke, which would be a fresh take on their characters.
In the fanfiction 'Sakura's Redefined Heart', Sakura has an epiphany that her love for Sasuke was more of an infatuation. She begins to see the flaws in Sasuke's character that she had overlooked before. She then devotes herself to improving the medical facilities in the village and forms a bond with a new character introduced in the fanfiction, a wandering ninja who shares her values of peace and helping others.
Sakura's ability to forgive and still care for Sasuke despite his past actions could also make him proud. In many fanfictions, she represents unconditional love. This selfless love and her ability to see the good in him, even when he was at his worst, could make Sasuke proud of her as a person.
It depends on the specific fanfiction. Some fanfictions might explore the idea of Sakura no longer loving Sasuke for various reasons, such as feeling betrayed or simply growing apart. However, in many traditional Naruto - related fanfictions, their relationship is often a central and complex aspect that can go in different directions.
Maybe Sasuke sees Sakura's growth as a kunoichi. She has become strong and independent, and he admires that. So he wants her to be his.
Well, Naruto has a very warm and persistent personality. He's always there for his friends, and he has a big heart. In fanfiction, Sakura might see these qualities in Naruto and realize his true value. He's the kind of person who can make her laugh and feel safe, which could be very appealing compared to Sasuke's more brooding nature.
Well, it could be a misinterpretation on Sasuke's part. Maybe he thought Sakura was a threat to his goals at that moment in the fanfiction. He's always been very focused on his own path, and if he saw Sakura as getting in the way, he might lash out.
Maybe for the shock value. It's not the typical view of their relationship, so it can attract readers who are tired of the same old storylines.
One possible reason in this fanfiction scenario could be that Sasuke feels a stronger connection to Karin on a spiritual or power - related level. Karin has unique abilities that might attract Sasuke more than Sakura's medical ninjutsu. Maybe he sees in Karin a kindred spirit in terms of their past traumas and the way they've had to fight to survive. Also, Karin has always been very devoted to Sasuke, and he might be drawn to that unwavering loyalty.
In some fanfics, Sakura might avoid Sasuke because she's tired of his cold and distant attitude. She wants to surround herself with people who actually care about her and value her, so she chooses to stay away from Sasuke to find more positive relationships.
One reason could be Sasuke's continued pursuit of revenge. If in the fanfiction, Sasuke is so consumed by his need for revenge that he neglects Sakura and their relationship, it might cause her to stop loving him. Another reason could be that Sakura discovers a side of Sasuke she doesn't like, like a cruel streak.