I have yet to find a compelling use case, personally, for Facebook as something other than a Rolodex. Which is why LinkedIn seems redundant to me. I think my brain must be lacking some wires. I just don't get it. My wife does. But I don't.
You seem to be someone who does not feel a need to post your photos, videos, and daily statuses to share with others in your social circle. This is actually a good thing, especially when the endtime comes and all of these companies exploit the information that the rest of us are willingly putting on their servers.