@fentiger DID methods such as key: represent identity types. Right now the development is focused on simple key-based identity, but other kinds of identity are also possible with FEP-ef61. Managing keys is difficult and many people will probably want to delegate this task to identity providers. With DIDs this is very easy, just replace did:key with did:web.
Other DID methods can also be used, FEP-ef61 enables further experimentation with identity.
Of course we can invent our own standard for representing identities, but DID standard already exists and developers are more or less familiar with it. Some may dislike DIDs because they are associated with blockchain technology but this too shall pass. If technology works, eventually it will be widely accepted, and if not it will be forgotten. And in any case, DID standard does not depend on it, there are maybe 2 or 3 mentions of "DLT" in the entire spec.