As chonk said it's not treatable. The therapy is there to help with the PTSD that comes along with DID. I'd say with treatment and learning to communicate with alters if need be it's not a horrible disorder. Instead of a personality vanishing I'm pretty sure they either integrate or go dormant. Though I have heard of them figuratively "dying" or becoming unreachable. Saying that you need to help someone by getting rid of their personalities is.. just not a good way of looking at it and that's not how it works. That is who they are.
Oh yeah thank for y'all answer. It's actually great to see that the treatment is not to make the other personality disappear. It's quite sad when one of them vanish :(. Also chonk, I think you did a great job explaining it. I really like to talk about this kind of subject.
I wonder if someone is expert here cause I want to ask some questions. Is DID really that treatable? Are some of people with DID really wanted to be treated? I kinda assume actually that it's really fine to have multiple personality because I saw some youtube video of how people live with DID and they're actually doing fine even with their multiple personality. They doesn't even look like they want their other personality to vanished etc. I wish I'm not offending anyone, I'm just really curious.