Why do digital credentials need to be revocable?

Credentials can be things like a driving license, or a qualification certificate. But what happens if you find out that someone cheated, or didn’t keep their training up to date? There needs to be some way to revoke a credential. Otherwise it will be valid forever, possibly damaging the trust of the attester. That’s what KILT provides – a way to produce digital credentials that can be revoked if and when necessary.