Thieves' Cant is called Thieves' Cant because it is associated with thieves and the criminal world. Of course it's biased.
It is easily argued that the "language" should be more broadly defined, or that it should be used for any given group that may have a method of nonverbal communication. That doesn't mean Thieves' Cant should be co-opted by random hunters or the Wolfswood Rangers or dwarven tunnel scouts or halfling outriders or Toranite temple guards or any other group that players can imagine may use a secret sign code. It's actually much more fun to make your own code or actually act out the signs in emotes anyway, as I did for Jennara before the sign language ear existed. As nice as the ear is, signing has never been as fun since.
It should not be limited only to criminals, and I have never suggested so. It is the Thieves' Cant, though, and should only be used by those familiar with the criminal world in some way, be they criminals themselves or law enforcers who are familiar with criminal ways or just barmen in shady establishments where it's a good idea to know what's up. If it should be more broadly applied, a name change would be nice. That would, though, steal a lot of its RP flavor away and do exactly the opposite of what Lord Dark was suggesting appropriate by making it more likely that any given character, Rogue or not, knows the mysteriously universal proto-sign language.
And, now that I think about it, the emotes from the Thieves' Cant ear aren't all silent, anyway. It is not a silent form of communication.
