Signatures _aren't_ hard proof, they're absolutely contestable. Images and videos once were hard proof, but now are becoming contestable.

I wonder how long it will be before we see journalism-focussed photography equipment automatically generating a secure cryptographic signature for each shot. A particularly fancy implementation could be signed by both the manufacturer and the photographer, offering two assertions the shot is valid and undoctored. Going back to a reputation system still isn't great, but it's a lot better than a "pre-industrial state of discourse"

Anecdotally,

Whenever I receive a signed-for delivery, I'm asked to provide my name and attempt to sign on the proffered touchscreen device - invariably scrawling a shape that in no way resembles my actual signature.

I recently accepted a new role, and as part of the on-boarding digitally signed my contract by typing my name into a text box marked "Digital Signature" - I'm kinda assuming it's just a regular input box with added legalese.

Signatures are absolutely no longer proof of anything, simply a token gesture with perhaps a dash of security-by-fud tacked on.

I think a signature is less about proof of identity, than proof of consent.

>why are signatures and written documents still taken as proof

I always thought this was tradition / theatre at this point.

On most important documents, they have to be notarized, which is a second level of authentication.

For any important document, the signing is almost always witnessed by someone else. My understanding is that the act of signing is primarily the legal act of accepting the document, not a security mechanism. The signature provides a quick reassurance that a document has been accepted, but if there were a real dispute, the witness could be asked to testify.

Yes, almost always signatures are only going to be relevant to civil cases, which are decided on the balance of probabilities. So all the evidence introduced is about pushing those probabilities around. A signature is neither necessary (except in some special cases) nor sufficient but it will usually be evidence for "acceptance", one of the main parts of a contract in law. A witness would shore up that piece of evidence but it rarely comes up. In most cases acceptance is not disputed because doing things you contracted to do is also pretty good evidence for acceptance and that's usual. e.g. if you're in court over a car lease, the fact you paid the first three months and drove the car is usually going to be more than enough "acceptance" for a court even if the signed document has been lost.

In current use, a physical signature doesn't really verify identity or authentication (i.e. that it was you who signed the document) but rather intent and consent - i.e., assuming that it's your freely given signature, this "ritual" marks that you intended to approve that document as opposed to words and gestures indicating that yes, maybe this is the right decision for some future time but might still want to think about it.