More in the way that we assumed that "people like to communicate", so we built something that looked like the real world. But what people really want to do is share experiences and talk about that, which is why everything from sports to bars exist. People probably don't "communicate" as such in WoW (while I'm sure it happens), but they don't in the real world either.
When used as a communications platform, it's a text/voice communication system with an unrelated 3d game you can play to keep from getting bored.