It could be due to Sakura's feelings for Sasuke. If she's overly focused on Sasuke and Naruto gets in the way of her plans regarding Sasuke in some way, she might lash out and hurt Naruto without really meaning to cause serious harm.
Well, it could strengthen their bond. Naruto being hurt might make Hinata more protective and caring towards him. This could lead to Naruto realizing Hinata's true feelings for him more deeply, and in turn, he might start to see her in a new light, growing closer to her.
One reason could be for the sake of the Naruhina relationship. To make Hinata seem like a better match for Naruto, the writer might make Naruto hate Sakura. For example, if Sakura is written as being too pushy or bossy in the fanfiction, Naruto could start to dislike her.
Well, in Naruhina fanfiction, the idea of Naruto hating Sakura can be a device used by writers. It could be due to jealousy in the context of the story, like if Sakura is shown as being too close to someone Naruto doesn't like. Or it could be a misinterpretation on Naruto's part of Sakura's actions. But this is all part of the fictional world of fanfiction, and not a given in the overall Naruto universe.
Misunderstanding is a common theme. For example, Naruto might misinterpret Hinata's actions or vice versa, leading to emotional pain. Another theme is sacrifice. One of them could sacrifice something important for the other, but it causes hurt in the process, like giving up a dream.
In a hurt comfort fic, perhaps Sakura has an emotional breakdown after a failed mission. Naruto finds her crying alone. He sits beside her and just listens as she pours out her frustrations. Naruto then shares his own insecurities, like how he sometimes doubts if he can really become Hokage. This mutual sharing of pain and comfort brings them closer, strengthening their friendship in a way that goes beyond their ninja duties.
In some fanfictions, Sakura might accidentally hurt Naruto during a training session. Maybe she uses a new jutsu she's not fully mastered and it goes wrong, hitting Naruto instead of the target.
One common theme is misunderstanding. Often, Naruto may misunderstand Sakura's intentions or vice versa, which leads to one of them getting hurt. For example, Naruto might misinterpret Sakura's concern for him as pity, and his reaction could hurt her.
Well, in some Narusaku fanfictions, Sakura might hurt Naruto emotionally by choosing Sasuke over him repeatedly. This can make Naruto feel rejected and unloved, causing him pain.
One of the themes is self - discovery for Naruto. When Sakura hurts him, he might start to re - evaluate himself, his relationships, and his place in the world. For example, he could wonder if he was too naive in believing in their friendship. Another theme could be the consequences of power. Maybe Sakura, in her pursuit of power or in using her power, ends up hurting Naruto. And the theme of redemption might also be there. If Sakura realizes she has hurt Naruto, the story could be about her trying to make amends.