There is a very famous quote by George Santayana, who was a famous writer and philosopher:
Those who cannot remember the past are condemned to repeat it.
This sums up very well the reason we study history. As individuals, we cannot possibly remember all of the past, going back thousands of years in recorded history, but what we can do is learn about the past, by taking history in school, finding out what individuals and societies did in earlier times, so that we can learn from the successes and failures of that past. There are so many examples of how history can help us this way.
For example, as we discover how various societies have been governed, with kings or queens or dictators, we learn what kind of governments have and have not worked. We have learned that pure socialism and communism have not been effective means of government, creating more problems in society than they solved. We learn what happens to a country in a dictatorship. We learn what happens if a country is a democracy. All of these are lessons we learn from history, lessons that help us to make good choices.
We learn by studying the history of economic systems what has and has not worked. By studying command economies and capitalistic economies, we learn from the mistakes different kinds of economies yield. For example, command economies usually result in shortages of goods and services, and unregulated capitalism results in socioeconomic instabilities.
By studying history, we learn about the necessity of war and the foolishness of war. Some nations began wars to their great regret, while we conclude that other nations have entered into war for reasons that seemed good and just. The more we learn about the history of war, the more intelligent decisions we can make about it.
When we study everyday people in history, we learn a great deal about how people have and have not changed. We know that people thousands of years ago struggled in their lives, were frightened in battle, and loved their children. But we learn also how far we have come since early times, how much easier our lives are today. These are valuable lessons for all of us, what we cannot change about being human beings, and what we can change as well.
History is the collective wisdom of the ages. If we do not know it and understand it, each of us is starting all over again, without the advantage of knowing what has gone before. It would be like being a child who had no parents to teach it how to walk, what to eat, or what is of danger. Without learning history, we are all parentless children!