In movies and tv we see it being used an excuse for murder. And it's always a case of extreme DID where the character becomes a full new person but doesn't remember the other person or people they become.
It asks a lot from people to believe in such a thing.
I have trouble with that extreme version of it myself but I do know the lesser version of DID as I have suffered from it myself and I don't see it as being a whole new person as much as I do see it as one immersing them self very deep into an alternate reality to escape the one that is too painful to bear.