The statement "nobody but the recipient can decode the packets" is meaningless if there are no bounds on who "the recipient" is. The analogy for the first case

The statement "nobody but the recipient can decode the packets" is meaningless if there are no bounds on who "the recipient" is. The analogy for the first case is more like "The postal service guarantees that it won't be opened before whoever is reading your mail opens it", which is clearly a pretty meaningless guarantee.