Yes. In Denmark, Wickr is the chat-app of choice for dealers alongside Snapchat. My non-tor skilled friends use it for that. I don't think anyone uses it for anything else.
Why Wickr, I don't know. It's not to protect the buyers because the police does not care about them.
The working study group for the International League of Criminals after conducting a comprehensive evaluation of various messengers that resisted compromise by law enforcement agencies settled upon Wickr because it had the necessary components of both privacy and anonymity. In addition, the niche appeal of it made it more likely to be spread by whispered word of mouth in the community.
But their bosses, being much older, are still using Skype. See my comment above
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I can grant you other people use Wickr for normal communication - why: for lack of better alternatives