I'm afraid there's also a misunderstanding how the real world works. Cryptographic and real-world plausibility are two entirely different things.
People get blackmailed, shamed, hurt and even killed over mere rumors, speculations and suspicions. As long as people believe in something (because something merely look plausible), there's no need for a fancy crypto to prove some machine sent some email. I'd dare to say most people don't even understand what cryptography is and what digital signatures really are (who signs what and what exactly this means).
I'm yet to hear a story of, let's say, a brave dissident who got out of jail because of cryptographic plausible deniability property making their oppressors unable to prove authenticity of some leaked or intercepted correspondence.
Read up on the Hunter Biden emails. After a DKIM signature was verified, the perception of a large number of people (including right here on HN) went from "this cache of email is probably total fiction" to "they likely do have access to at least some of his emails".
People get blackmailed, shamed, hurt and even killed over mere rumors, speculations and suspicions. As long as people believe in something (because something merely look plausible), there's no need for a fancy crypto to prove some machine sent some email. I'd dare to say most people don't even understand what cryptography is and what digital signatures really are (who signs what and what exactly this means).
I'm yet to hear a story of, let's say, a brave dissident who got out of jail because of cryptographic plausible deniability property making their oppressors unable to prove authenticity of some leaked or intercepted correspondence.