I can't see why should I, and I'm not excepting everyone who I "fan" to add me as a friend. To me the thing about adding people is that it is easier to keep up with what they have written lately that way. People who seem to have interesting lives to share in their stories or people who just have talent for writing. Or people whom I have in my opinion something offer to, in comments, discussions or otherwise.
Exchanging messages would be nice, but not all that important to me. I'm here mainly in order to both read and maybe offer someone something to read as well. People are interesting, and for me this site and most of the Internet is just a big collection of novels, the 'slice of life' kinda novels. I think those are the best of literature; the themes of stories about real life are usually as rich in themes as the most classic pieces of literature, and the plot is hardly predictable.
So, if I would happen to add some of you without starting a conversation... well, now you at least know why.