Based on, I dunno, browsing the web? Seeing an occasional TV ad on an airport TV? I don't think it's quality stuff or anything but if you found these confusing, I suppose we move in entirely different media environments.

Edit: And, of course, it's also a typical way we often talk about generic scenarios outside of advertising. Alice and Bob are not real people trying to establish secure communications. There is no specific Johnny who can't read, etc.