The question as to whether DID is real is a complex one. Not because it's 'real' in the sense these people have different personalities they can't control but in the sense they choose to behave as if they do and it's common enough to be considered a disorder.
I am old, and this is cranky, because I, indeed, happen to be old and cranky:
DID is
not real. There is, very plainly, no such thing.
There is no disorder that causes someone to "fracture" or "splinter" into multiple, task-specific sub-personas. It is "real" only in the sense that someone can be induced to believe that it is real, and that they have such a thing, through
profound psychiatric abuse.
The most charitable possibility is that DID is a culture-bound disorder that only afflicts the west, like Dhat in the Indian subcontinent, Koro in China, and so on. I am of the opinion it does not deserve even that level of regard. It is a thing that did not exist outside of America until American-trained practitioners began to diagnose it. It is not a coincidence that the most vocal proponents for DID are, also, the most vocal proponents for other forms of abusive nonsense, such as 'recovered memories' and 'Satanic abuse.'
No one has DID until they are under the care of a practitioner who believes in DID.
Twenty years ago, it was being consigned to history as a particularly embarrassing example of what happened as the science of the human mind was being codified. Today, it is one of the many abominations that a generation of idiots has chosen to dig out from the trash.