Why is no one talking about using zero knowledge proofs for solving this? Instead of every platform verifying all its users itself (and storing PII on its own servers), a small number of providers could expose an API which provides proof of verification. I'm not sure if some kind of machine vision algorithm could be used in combination with zero-knowledge technology to prevent even that party from storing original documents, but I don't see why not. The companies implementing these measures really seem to be just phoning it in from a privacy perspective.