Re: You can read my SMSs but you can take my WhatsApps from my cold dead hands
While you're mostly correct above, bear in mind ciphers and encryptions existed before the mail service even did. If you didn't want someone to know what you were saying to a friend, you might write something that would be either unintelligible or downright misleading.
This practice continued well into the 20th century. Those Chicago gangsters from the movies certainly weren't wanting to warm their cold hands with their "heaters" etc. after all...
At some point computer-based encryption allowed people to conveniently communicate in plain text without worrying about such codes and ciphers, since the machine would encrypt the communications for them. The larger battle that needs to be won, immediately, is to enshrine the use of client-based encryption (e.g. open source) as a fundamental human right. After all, encryption was available for use for the past several centuries, there is a strong argument to be made that it cannot be banned without a reworking of the entire social contract (and simultaneously plunging the nation into an agrarian dark age).
As far as information going dark, that's been a problem since written records started. Fire and paper don't get along very well, and human memory is so ... fickle.