Some of the top reasons for me are:

Because it is easier to manage physical pain on the outside than emotional pain on the inside. People who SI have not learned better and more effective ways to cope with difficult, painful, and overwhelming emotions. You can hold them in for so long before they have to go somewhere.

To keep from doing something worse, like hurting someone else, or suicide, or more harmful self-destructive behaviors (could be substance abuse, eating disorder, gambling, worse SI than what was done, ...). When emotions have been held inside for a long time, they reach a point where they just explode, and that is really scary. I would say that most self-injurers do not want to take out their anger on other people, especially people they love, and they are afraid of what they might do, so they hurt themselves so that the feelings have someplace to go.

To have control of something. When you feel out of control, or have not been given the opportunity to be in control of your own life, you look for anything that you can do that you can control. Especially when someone else has hurt you and you couldn't do anything about it. This is something that we are in charge of. We can choose how much, when, where, and how we hurt.

To prove that our feelings are real. Every self-injurer probably has a history of having their feelings invalidated by someone they cared about. With a lot of emotional invalidation, we start to question our own feelings. Maybe they are right, and I don't really feel the way that I do, or have any legitimate cause for all this anger. If we can see it, then it must exist. This can be proof for ourselves or proof for someone who tells us we are just being a baby or selfish or blowing things out of proportion. Even if what we want is to prove the validity and existance of our feelings to someone else, we might not ever actually show it to them or tell them about it.

To get help. What is so bad about wanting attention, anyway? Attention is a legitimate human need. It is okay to ask for attention. To self-injurers, though, it probably doesn't feel okay to ask. We feel like we are not allowed to need anything. Sometimes SI is a cry for help. And that might be a better way to word it. I can't speak for everyone, but my SI did escalate when I passed the point of what I could deal with (or avoid dealing with) and manage on my own, and I wasn't getting enough help, and didn't feel like anyone took me seriously if I said anything about it. SI was proof that I really did hurt and that I needed help. This is sometimes a little bit similar to Munchausen's, where people make themselves have symptoms of serious illnesses so that they can go to doctors and be treated.

And of course there are many more reasons, as each self-injurer has his or her own. We might have some reasons in common, and others might be unique.

Rap