Not letting you see my face is actually about respect: I don't want people to embarrass themselves trying to read my mind based on what my face is doing while ignoring what I'm actually saying with my words. I've found it's usually people with a need to see a face (or worse, eye contact) when talking who refuse to trust my words in favor of what they assume based on "body language" (at best a weak signal often given too much weight), so it's better for everyone.