I searched through my posts and realized I don’t really have a cope shipping masterpost? So here’s the main reasons I’ve heard:
Catharsis: a literally ancient tradition of using fiction to help you feel difficult emotions, like fear, anger, sadness, or guilt, without having to confront them too directly. Sharing those emotions socially can also reduce the impact and lighten the load. For people who are dealing with totally overwhelming emotions because of trauma, catharsis is a way to bleed some of it off, maybe even in fictional circumstances similar to their trauma, allowing them to talk about it and feel it when they’re not yet ready to confront it directly. Probably most angst-shipping is in this category, and it’s by no means limited to trauma victims; anyone can benefit from and even enjoy catharsis.
Narrative Therapy: more directly relevant to survivors, this is the process of shaping what happened to them into a coherent narrative, and sorting through the ambiguities and confusion. While often “angsty”, it doesn’t have to be: I can personally testify that frequently narrative therapy is just as important for dealing with and rationalizing the positive emotions I felt during trauma.
Projection: anecdotally, many people use fiction to regain a sense of power that was lost during trauma, especially sexual trauma. These fics can go a lot of different ways: they may be virtually indistinguishable from the trauma, and overlap with narrative therapy. or they may go radically different ways: for example, the victim becoming the aggressor, or alternately the aggressor being much more aggressive and violent than they were in real life. These kind of what-ifs are a natural part of trauma, and not unhealthy if they don’t consume your life or prevent you from dealing with what actually happened.
Kink: While it’s not universal by any means, sexual trauma (especially CSA) can have a significant effect on your sexuality. Rape fantasies, CSA fantasies, all variety of transgressive sexual fantasies are more common among survivors. These fantasies are common, not harmful, and eliminating them isn’t a part of recovery unless the survivor is very distressed by them. Fiction is an easy, safe way to engage in those fantasies without creating more victims or attempting anything risky in real life.