Oh how I do agree with you, Art!
About fifty years ago I, as a member of the UCLA Daily Bruin, had the assignment of interviewing English Dept. faculty regarding their research projects. One--I forget who--was publishing the correspondence of and between Wordsworth and Coleridge (I think that's who). I marveled that such would have been saved, collected and commented on two centuries later. In the age of the telephone and Skype, I'd be surprised if such personal correspondence of today will be retrievable in another two hundred years.
But on the bright side--and I know this is a long digression--last week I did come across, on a blog, six exchanges between two authors
discussing a topic of mutual interest about six years ago. Interestingly, it began with some antagonism on the part of the initiator, but by the last posting they had reached mutual respect for the other's position, while yet disagreeing with each other on many points [ah that that could happen at Mudcat more often!]. I printed it out because I was intrigued both by the topic, and by their literate arguments So, maybe such correspondence can be available for future study.