History and The Past

Why are some facts about the past recorded and remembered and others not considered worthy of committing to memory?

History is a selective retelling of events, dictated by the narrative a society is trying to push. Often facts are overlooked because they do not aid this narrative. If all facts about the past were remembered and retold there would be no clear pattern or understanding of how one event triggers another. History is an attempt to find pattern and coherence in a chaotic, complex sea of facts.
Facts not told within the mainstream narrative are not always erased, and are usually retold in alternative narratives. These alternative narratives often form the base of off-centre ideologies and social movements, such as Feminism, Marxism, Anarchism etc.