I'm sorry people don't get it. To me, I see it as a way to get the emotional pain and trauma and feelings of helplessness on the outside. It's a proactive choice, not a positive choice, but something we do to retake control of the situation. Don't be offended because this isn't a perfect metaphor, simile actually, but kind of like people who turn anorexic and eat less and less and exercise more and more because the one thing they feel like they can control in their lives is their weight or the way they look. If we can't get rid of feeling terrible inside, at least we can dissociate for a while by creating physical pain.
As with depression, bipolar, schizophrenia, and SI, it's never a cry for attention. When I was a little kid my dad always moaned at me for being full of "self pity" and "moping." I was physically and sexually abused and didn't know why I was so depressed all the time and couldn't join in with the other kids in normal activities. It all seemed so pointless to me. Anyways, my sadness and withdrawing from life had nothing to do with wanting attention. It was me perplexed and unable to process all of the pain. And I think that's what's happening much of the time in SI. You are loved and understood here.