One possible reason could be that Snape is starting to see Harry in a different light. Maybe he realizes that Harry has been through a lot and has a moment of empathy. It could also be a sign of a deeper, unspoken connection developing between them in the alternate universe of the fanfiction.
Perhaps Snape is under some sort of magical influence that compels him to be more nurturing towards Harry. In fanfiction, all sorts of magical anomalies can be used to drive the plot. Or it could be that Snape is trying to gain Harry's trust for some ulterior motive, like getting information about Voldemort from Harry in a more subtle way.
One possible reason could be that Snape suspects Harry of something. Maybe he thinks Harry is involved in some sort of mischief or is in possession of something he shouldn't have. Snape has always been a bit of a mystery and is often distrustful of Harry, so this action might be his way of getting to the bottom of things.
One possible reason could be punishment. Snape has always had a rather thorny relationship with Harry in the original series. He might see this as a way to assert his authority over Harry. Maybe Harry has done something in the context of the fanfiction, like accidentally messing up Snape's potion ingredients or getting into an area of Snape's house where he wasn't supposed to be.
One possible motive could be Snape's complex relationship with Harry's father. Snape might see Harry as a way to get back at James in some twisted way. He could also be acting out of a sense of duty to the Dark Lord, believing that taking Harry by force is part of some larger plan to gain power or favor.
Maybe Snape suspects Harry of being involved in some sort of dangerous activity related to the Dark Arts. Pressing him to the wall could be a way to force Harry to come clean about his actions or any knowledge he might have. It could also be that Snape is acting out of his own insecurities and pent - up emotions towards Harry, which he has been suppressing for a long time.
One possible reason could be to get her attention in a very forceful way. Snape is often a complex character in fanfiction, and he might be trying to make Hermione listen to him urgently, perhaps about a dangerous situation in Hogwarts that she's not aware of.
Maybe Harry discovers something about his past, perhaps related to his parents, that only Snape can help with. Snape was closely associated with Harry's parents. He might know some secrets or have some information that could help Harry understand a family mystery or some hidden power within him.
It could be a plot device used by the author of the fanfiction. The touch might be used to create tension or an emotional moment between Snape and Harry. It could signify a turning point in their relationship, whether it's the start of a more positive understanding or the heightening of an existing conflict. For example, the touch could make Harry feel uncomfortable and lead to a confrontation later, or it could make him realize that Snape has a more complex side than he initially thought.
One possible reason could be Snape's long - held grudges and resentments. He had a complex past with Harry's father, James Potter. Snape might see too much of James in Harry and be unable to separate the two in his mind, leading to his rejection.
One possible reason could be that fanfiction often takes creative liberties that may distort the complex character of Snape that J.K. Rowling created. Snape has a very intricate backstory and personality in the original series, and fanfiction might simplify or misinterpret it.
One possible reason could be Snape's long - standing dislike for James Potter, Harry's father. Since Draco is from a pure - blood family like Snape himself, and Snape has a certain affinity for the pure - blood traditions and values, he might choose Draco. Also, Draco was in Slytherin, Snape's own house at Hogwarts, and he might have felt a stronger sense of loyalty to his house and its students.