The effort is not the point. Communicating is the point. Up until very recently, there was no alternative way to send a letter without writing a letter. There was no need to prove work was done. Cultural changes are much slower than technological changes, and thus things continue to be culturally required despite no longer being useful.

The idea that someone should waste their time to "prove their work" to you is absurd. If I knew someone did, I would deliberately go out of my way to bury information in excessive AI slop for them.