There was a lot written about the ease of wiretapping circa 1970, around the time that Nixon wiretapped himself. At that time it was notorious that people got trained by the FBI and CIA and then went into practice as ‘private investigators’, that was basically the story of G. Gordon Liddy and Nixon’s other ‘plumbers’, not to mention the people that General Motors hired to spy on Ralph Nader.
Really the invention of the transistor made it possible to make tiny bugs that you might look at and think are just a bit of nothing. In the 1970s people also invented other bugging devices such as an infrared laser that can pick up vibrations on a window from a long distance away.
Today if you have regular houseguests you might think very little of a strange phone being plugged in in some out of the way location, just one many devices that could be corrupted.
There is a tension though between gathering information an acting on that information. Back in the USSR they hired a lot of people to spy on other people, they had a house full of people spying on Andrei Sahkarov. This is both a symptom and a cause of an unproductive economy.
If you really have to physically harass or jail people then the ability to use information doesn’t scale w/the ability to gather it. If you can discriminate against or harass people entirely online (e.g. ‘social credit score’) that is something different.
A tension behind all these things is that you don’t want to reveal your methods, there are many criminal cases that get dropped because the people involved are not important enough to be worth scaring other people into better opsec. I found nothing surprising about the Snowden ‘revelations’ (if it had been revealed that the NSA was not doing that it would have been a scandal because what do we pay them all this money for?) but it did lead to https everywhere to protect us not just against the NSA but many organizations and individuals who have far worse ethics. (There was that time I turned on a packet sniffer on WiFi on an academic network and got about 20 email passwords in a minute, which I deleted right away.)
Personally I think stolen documents are much more likely to be used against you then surreptitious audio recordings, I would not use email for an HR problem or anything where there might be a lawsuit. I cannot see it how people sext because my reading of Dangerous Liasons is that those people came to a bad end not because they were promiscuous or sadistic but because they wrote it all down.