This article is a great explainer of the basics underlying anonymous credentials. I look forward to the promised follow-up explaining real-world examples.
The key issue however is trust. The underlying protocols may support zero-knowledge proofs. But as a user I'm unlikely to be able to inspect those underlying protocols. I need to be able to see exactly what information I'm allowing the Issuer to see. Otherwise a "correct" anonymous scheme is indistinguishable from a "bad" scheme whereby the Issue sees both my full ID and details of the Resource I wish to access. Assuming a small set of centralized Issuers, they are in a position of great power if they can see exactly who is trying to access exactly what at all times. That's the question of trust - trust in the Issuer and in the implementation, not the underlying math.
Not for trains - there's a shared expectation that pedestrians should not access the track.
Similarly, not for a freeway.
Where some feel the balance is wrong, is at local-level streets. Today the assumption in most places is that cars have total right of way, and pedestrians must keep clear. It doesn't have to be that way. In a residential area, it's quite feasible to say all road users have equal right to use the space. And in that circumstance, put the onus on the car user (wielding a heavy, dangerous weapon) to not hit other road users.
The key issue however is trust. The underlying protocols may support zero-knowledge proofs. But as a user I'm unlikely to be able to inspect those underlying protocols. I need to be able to see exactly what information I'm allowing the Issuer to see. Otherwise a "correct" anonymous scheme is indistinguishable from a "bad" scheme whereby the Issue sees both my full ID and details of the Resource I wish to access. Assuming a small set of centralized Issuers, they are in a position of great power if they can see exactly who is trying to access exactly what at all times. That's the question of trust - trust in the Issuer and in the implementation, not the underlying math.