How can steganography be useful in a social networking and sharing website like Facebook or Reddit?

The point of steganography is to hide useful messages in other messages so that no one suspects the message to contain secrets and tries to crack the message.

The catch is that the recipient should know what that such a message is to be expected and how to decrypt it (find the hidden message).

Steganography helps protect the message while in transit.

In today's social networks and sharing websites like Reddit and Facebook, communication between two people is easily possible with private messages. These private messages are sent encrypted anyway and steganography isn't really the most reliable way to proceed with.

So how can steganography be really useful?

Is there a use-case where one posts a "steganographed" message on Reddit sub-reddit or a Facebook wall?