What is this thing with calling people by their first name without their permission?

What happened to courtesy? People address me by my first name as if they were a personal friend or member of my family when they don't even know me! Why is it considered acceptable to take such familiarity without even asking? And people get ugly when I correct them. What makes it all right to address a person any way you want without consideration of their preference? Perhaps they make the mistake of thinking they are being friendly. That is a mistake. Calling someone by their first name does not make somebody their friend.