Cause it's just a tool. A tool that promotes laziness in communication and personal contact. All for the low low cost of all your privacy so they can sell you to whoever. It's a convenient tool though
Most of my friends don't live near me. I stay updated on their lives via Facebook. What's so sad about that?
The point of tools is literally to enable laziness. Feel free to go back to the telegraph if you really want to work harder.