In a world of "don't talk to strangers," we all stand isolated, back-to-back, in a crowd. Afraid to look into the eyes of those around us, afraid we might find similarities in those eyes.
Afraid strangers may become friends. For if strangers become friends, then they aren't so strange after all.
And if they are still strange, then, we, too, must be strange as well.
And if this is so, then there is nothing to fear beyond our own capabilities, quirks, and quandaries, and that thought is scarier than the thought of strangers.
So we choose to remain isolated in a crowd of familiar eyes.