Why do people carry on personal conversations on their Facebook pages?

If you want to have a personal conversation with someone that is just between the two of you, there are many ways to do that. You can call, text, email, or send a message via Facebook. Hey, you can even pay them a visit!  What you don't need to do is carry on the conversation through their Facebook page so hundreds of other people can view your conversation! Years ago, I mean MANY years ago, when the thought of actually having a computer in your home was science fiction, we had something called "party lines". Party lines were when you had several families on one telephone line. If you went to pick up the phone to call someone, your neighbor might be on the line. You could either put the phone down and wait to use it later, or you could be "bogus" and invade their privacy by listening in. My point is that conversations between two people on Facebook is like being on a party line. I don't know about you, but I feel like I'm spying by reading it.