I think some of the appeal is probably that the listener need make no outward sign that a message has been received. There is also very little papertrail or ot

I think some of the appeal is probably that the listener need make no outward sign that a message has been received. There is also very little papertrail or other evidence that anything has happened, or about the content of the message. It self-destructs forever, even more securely than Snapchats ever could.