"If people have a conversation in a pub or on a park bench, then law enforcement can surveil them individually or bug the venues in a targeted manner."
My home internet connection could have spies from 30 different countries all over it and I wont see anything. If I'm sat on a park bench then anyone with a Russian accent asking for directions to Salisbury Cathedral is going to stand out somewhat.
If you watch enough English language spy movies you will know full well that a Russian spy has a Scottish accent. So do Russian submarine captains. Funnily enough a British spy and a Russian submarine captain were played by the same actor - Sean Connery. Russian spies are played by less posh Scots.
Hollywood and co. doesn't get out much or something.
My home internet connection could have spies from 30 different countries all over it and I wont see anything. If I'm sat on a park bench then anyone with a Russian accent asking for directions to Salisbury Cathedral is going to stand out somewhat.