In my opinion it could be because DPDR is extremely difficult to explain, it seems too abastract and people who have never had it cannot picture what it could feel like. A lot of mental disorders are like that, but I think almost all of them are probably much more spectacular or visible form outside.
Also I don't think DID could take the spotlight away from DPDR for most people, since most people probably don't know that DPDR is a dissociation phenomenon.
Also I don't think DID could take the spotlight away from DPDR for most people, since most people probably don't know that DPDR is a dissociation phenomenon.