There's a lot that could be said. Information on everybody goes everywhere now, with or without your consent. Privacy and anonymity command a premium, where they're available at all. Increasingly, it takes money and clout to have any. That being the case, why would you just give it away?
But, personally, I think the question posed in the thread subject line itself incorporates a subtly twisted rationale.
The real question should be, why are you uncomfortable even talking to someone without knowing their "Name, location, age, and even daytime job"? How relevant is any of that? Do you really have to pigeon-hole people to even converse comfortably, and, if so, what does that say about you?
I don't think it's the people interested in protecting their privacy that need to be on the defensive here. I'd much rather see the people who are uncomfortable with the privacy of others have to justify their own position.
Personally, I don't see any need to pry. Discourse can stand, or not, on it's own merits.