You don't have to imagine contrived futures to see why privacy is important. You only need to look at the present, or even easier, the past. Rational people dominate neither governments nor society. Privacy and secrecy are the first line of defense that the oppressed have against prejudice.

As far as "enemies trying to ruin lives", it's wonderful that you are so privileged as to even be able to think of that as "contrived", but you would do well to pay attention to other people's situations.