I think we just see this differently, it isn't inherently positive or negative in my view, it just *is.*
Beyond that, your statement about keeping white lies to a minimum implies that people really know themselves. That people can articulate that they do x/behave like y/dress like z (or whatever) because they want to look/feel/hide something. My experience is the opposite, nobody is totally self aware and people act on instinct whether it is in real life or how they portray themselves on social media. Further, I would argue that everybody has the right to promote whatever image of themselves they like, provided it isn't harmful to them or others. I don't want to get into a specific debate about that, because I am sure people could prove me wrong, but as a general principal if I want people to think i am cool like Fonzy, then I am free to make him my avatar and say "AAAAAYYYYY."
As for you question I am not sure I have an answer. I have conversations all the time of varying levels of brutality, pleasantness and secret divulging but I think that is different from what you are asking.
It is interesting though and I am enjoying the discussion - a question for you, Mybudgee: (Roughly) How old are you? Is it possible that the change in type of conversation, the rareity of that type of conversation, are features of the fact that it tends to happen more when you are younger and you and your peers are getting older? I haven't thought this through, but I have a theory that the layers we add to our projected image thicken and increase over time, becoming more subtle in some ways, and less like to be pierced by conversation the way you describe.