Most credentials are checked once, at the moment they are issued.
A background check runs, a status is confirmed, a document gets signed.
The system records that everything was valid at that specific point in time.
The problem is that circumstances change. Someone qualifies for housing assistance today and loses that eligibility in three months.
A business license is valid at issuance and lapses six weeks later. The original credential still exists. It still verifies correctly. It just no longer reflects reality.
This is the gap I keep thinking about with $SIGN . The protocol does one thing well it records that a specific attester made a specific claim at a specific moment, and that record is cryptographically immutable. You can always verify the original attestation.
What the attestation cannot do is update itself. The schema captures what was true at issuance. It has no mechanism for what happened after.
Most real world eligibility disputes do not live at the moment of issuance.
They live in the six months that follow it.
Whether an on-chain attestation layer can ever fully address the temporal dimension of credential validity is a question the space has not answered cleanly.