Life is the way it is now because of how things used to be. Every person has a history. So does every relationship, every building, every metaphysical concept. You cannot simply look at a given scene or person and understand what is going on or what people are thinking unless you know all of their contexts. Otherwise, you can make incredibly logical, yet utterly wrong assumptions.
As a writer, this is why it is crucial to give your audience the proper context of a situation before you elaborate on it. Otherwise, you will leave people scratching their heads the whole while through.