One reason could be character development. For Draco, crying because of Harry can be a turning point. It can make him re - evaluate his relationship with Harry and his own actions. And for Harry, it can also be a moment of self - reflection. Maybe he realizes he's been too harsh or misjudged Draco. Plus, it gives the writers a chance to show different sides of these well - known characters in the Harry Potter universe.
Maybe Draco says some really mean and hurtful words to Harry. For example, he might make fun of Harry's family situation, like his parents' death or his relationship with the Dursleys. Words like that can be really cutting and could easily make Harry cry.
Well, it could be for character development. By having Draco hurt Harry, it shows different sides of both characters. Harry might show his resilience, and Draco could be portrayed as more complex, not just a one - dimensional villain. Also, it can make for an interesting twist in the fanfiction story.
Some writers might do it for the sake of creating drama. By making Ginny a 'villain' of sorts, they can add more conflict to the relationship between Harry and Hermione.
One reason could be to explore complex character dynamics. In the original 'Harry Potter' series, Snape has a very ambivalent relationship with Harry. By writing about Snape rejecting Harry in fanfic, writers can dig deeper into Snape's internal conflict. He has his own grudges and loyalties, and this rejection could be a way to show how his past and his own sense of self prevent him from fully accepting Harry.
Some writers choose this plot because it creates a lot of drama. Harry and Draco are from rival houses at Hogwarts, so forcing them into a marriage is a huge contrast to their previous relationship. It also allows for a lot of character development as they have to overcome their differences.
Some writers might do it to explore the darker side of human nature and raise awareness about certain issues.
At first, it would become more strained. Harry would likely be angry and hurt by Draco's actions that made him cry, so he might avoid Draco even more than before. He might also be more on guard around Draco, not trusting him at all.
In the fanfiction 'The Lost Friendship', Harry makes Draco cry when he chooses his other friends over Draco in a crucial moment. Draco had always secretly hoped for a real friendship with Harry, and this rejection is too much for him. Also, 'The Harsh Truth' is a fic where Harry, in an attempt to make Draco see the error of his ways, tells him some brutally honest things that make Draco realize his own insecurities and he ends up crying.
Some writers might choose this scenario for the shock value. It's an unexpected and somewhat controversial action that can immediately grab the reader's attention and make them want to know more about what led to it and what will happen next.
Some writers might do it for shock value or to stand out, not realizing the negative impact. Also, a lack of awareness about gender equality issues could be a factor.