1. backups and account recovery: We’re working with humans here. They will lose their keys in great numbers, sometimes into the hands of malicious actors. How do users then recover their credentials in a quick and reliable manner?
2. Fragmentation: let’s be optimistic and say digital credentials for drivers licenses are given out by _only_ 50 entities (one per State). Assuming we don’t have a single federal format for them (read: politically infeasible national id) how does facebook, let alone some rando startup, handle parsing and authenticating all these different credential formats? Oh and they can change at any time, due to some rando political issue in the given state.
OP, you clearly know all this, so I’m just reminding you as someone down in the identity trenches.