They'll do it every time

Old movie fans have no doubt noted that people who are being followed invariable, when they get into a cab, shout the destination before they get in, thereby allowing the other person to hear clearly their destination (and in turn shout, "Follow that cab!") They just as easily could have given the destination in a lower voice after they closed the cab door, and lost virtually no time - but that would not have prevented one of the fun features of the movie. But they almost always shout the destination from the sidewalk.