I disagree, I don't think there is any need for proof of identity to not be voluntarily relinquishable.

I think relinquishable credentials are quite useful for a number of delegation related uses - but if they are relinquishable then they need to be expirable as well.

The guy with a knife won't ask for proof of identity that he knows you can't give up.

If a guy with a knife wants my password I'm going to give it up and walk away alive, then try and recoup the loss of whatever I gave up... maybe I get the debit against an account reversed or purge recent account activity from social media.

There currently is nothing secret like that that I'd give up my life to protect, and I can't conceive of anything of such import existing... for those cases where the item is truly dangerous (like the nuclear football) then a guy with a knife being a threat is already a failure of security.

the guy with the knife is why fingerprints retinal or iris scans, and facial metrics shouldnt be used.

You may not be able to give these things but they can be taken, using that knife.

You don't even have to be alive for those things either.

This is how iPhone works today. Apple bricks your phone if it is stolen, as a disincentive against theft.