Definitely sometimes the case that it's secretive. I'd say I more usually use BCC like "You don't need to get involved in this conversation, but your name was mentioned and/or it's something you would want to know about." Kinda like covering your own ass so that somebody doesn't think you were talking behind their back or going over their head.
It's more like making a tape recording of a conversation you are having with someone and playing it to someone else who wasn't part of the conversation. And without the person being recorded knowing that you did that.
