People making that argument basically assume you are not already stuck in the honey if you go with your default ISP.
For instance, an embassy with clear telephone and telegraph lines knows they're being listened to, and subsequently is very careful about what they transmit. An embassy who has bought Crypto AG (https://en.wikipedia.org/wiki/Crypto_AG ) equipment thinks they are secure and transmits information they would never dream of sending if they knew they were being listened to.
Some jerk in a cube farm in Maryland does.