Better imho to ask: what user problem is DID solving? Because: if it's truly decentralized then there's no need to publish it. But publication is a core aspect of DID. That it must be published is a jedi mind trick that allows in "on a blockchain". Now we see the real problem being solved (not a user problem): need something published on a blockchain.
From https://www.w3.org/TR/did-core/#design-goals Decentralization | Eliminate the requirement for centralized authorities or single point failure in identifier management, including the registration of globally unique identifiers, public verification keys, services, and other information. Control | Give entities, both human and non-human, the power to directly control their digital identifiers without the need to re…
Not a chance really.
First, DIDs define a method behind resolving data be it use a website, use bitcoin classic, etc. There are over 100 defined, and only "web" and "key" (inlined data in the URI) have achieved interoperability.
Second, if DIDs define authentication then your Apple/Facebook/Google account will require to own the DID so that they can make sure the authentication requirements aren't rewritten to be too weak to qualify.
Third, DIDs used in that way are less privacy preserving than the existing system, since it is now a global identifier shared with everyone.