Why do we study it? we study history to know what it was like in the past and think of how did we change from past to present. what we get from history? we get information about who and what helped from then to now and how we became one country if you're talking about America.
History allows us to grasp transition and how it came to be the world we live in. The second explanation why history is unavoidable is that the first is closely followed by a matter of serious study. The past triggers the present, and so does the future.