When I was taking a class about Viking sagas, the professor told all of us students about the laconic style of writing. To put it simply, it's gearing a story towards a specific audience. The author will expect the reader (listener back then) to already know about certain people and other things specific to the culture.

The audience likes this type of story telling because it makes them feel smarter and a part of a community. They don't want to be retold the family lineage of a chieftain when they already know it.

It's easy to find this in many places today. If I said Bill and Monica, chances are you would instantly know exactly who I was talking about. You use it when talking to friends. There are also lots of acronyms found on the Internet, such as ROFL and LOL.