> Mail and Telephones were never at any point perfectly private
In principle they were not private but in practice they were because in most places the police had to realize that there was a conversation of interest, get a warrant, and use scarce resources.
Now the authorities are able to use machines to monitor traffic patterns for almost all communication the cost of interception is much lower.
The FBI has a history of illegal wiretapping as old as the organization itself. To keep it relevant to one of this weekend's big film openings, you can read all about how illegal recordings fed the hearings that stripped Oppenheimer of his security clearance. And the tradition extends to many other prominent figures including Martin Luther King. And today, this kind of surveillance continues through through more modern guises [0]. The volume of these 702 searches is dramatically down, which is good, but there is no reason to assume that it will stay that way.
Point being, one shouldn't assume that government agencies will adhere to the standard we might wish them to when choosing means of investigation or surveillance.
Oppenheimer was an obvious target, you and I are much less likely to be listened to when resources are scarce. So in Oppenheimer's time my communications would most likely have been very secure.
But now resources are less scarce and the task is easier so blanket surveillance and recording is more nearly practical.
In principle they were not private but in practice they were because in most places the police had to realize that there was a conversation of interest, get a warrant, and use scarce resources.
Now the authorities are able to use machines to monitor traffic patterns for almost all communication the cost of interception is much lower.