That’s already known. It’s why mingling at golf clubs and galas and charity events is important and why clustering in cities is useful. Generally, you can trust conversations you have in person to not be recorded and maintain plausible deniability.

Many companies and worse, public institutions around the world are moving to solidify the destruction of evidence with data retention policies. They may automatically delete any email older than 1 or 2 years, every instant message sent via corporate channels in 30 days, etc. as a "disk-space saving measure". Including backups! Anyone can see through that explanation since any CIO claiming cost savings come from the few tens of GB of archived Office Communicator chats should be politely invited behind the barn for a dramatic reenactment of an age old saying.

Scandals like Boeing's and others that shook trust in public institutions, most of which are required by law to make any such material available to citizens, just convinced them that proactive destruction of evidence is the way to go. This is not punishable by law. And when the requests for data do come in all the have to do is delay the process until the totally legitimate automatic policy kicks in and removes the last shred of evidence.

At this point only whistle blowers diligently collecting all the data before it's destroyed could still help in any way but this comes at great personal risk. And when tools like Signal are involved good luck with that, one would have to be part of every conversation.

Verba volant, scripta manent. Ancient Latins already knew the score. A lot of people initially refused to use emails in the ‘90s because they (rightly) perceived it as something written down and hence likely to be used to hold them to account - only people who grew up with IM have a more “disposable” view of electronic text.

I can assure you that any manager or owner on the planet, at some point or another, has a conversation where it is agreed that something will never be written down in any form.

Similarly, I have several friends working on wall street who flat out refuse to discuss anything related to a stock over email. Every discussion with them no matter how trivial is on the phone.

No paper trail, no investigation.

Don't phone, fax, and snail mail have more legal protections than email and other new communication methods as well?

In my experience, unwritten policies absolutely exist in major multinational corporations.