The main reason we study history is to understand the present. It is not possible to understand why things are the way they are without knowing the forces that led to the current state of events. For example, to understand many of the current geopolitical conflicts in the Middle East requires understanding the formation of Islam, including the early civil wars that pitted what became Sunni against Shiite. Next, the Islamic conquests of much of the Middle East and Mediterranean littoral, responded to by the Crusades, and then followed up by the creation of artificial national boundaries in the aftermath of World War I, shape many of the attitudes of Near and Middle Eastern nations towards the West. An additional layer of historical complexity is that Iran is the modern descendant of the ancient and powerful nation of Persia (which engaged in epic wars against Greece in antiquity), speaking Farsi, an Indo-European language (of the same family as French, Spanish, Sanskrit, and English), and following Shia Islam while the Sunni Arabs of Saudi Arabia have a nomadic Berber heritage, and speak a Semitic language (closely related to Hebrew). Without knowing all this background, many of the current regional tensions are simply not comprehensible, and yet, as a citizen and a voter, if you live in a democratic country, you need to choose political candidates in part by evaluating their foreign policies. Similarly, much of the history of your own nation has shaped its laws and political traditions.
Imagine that you were born and started off in life as a young person without any education about the past. Someone older than you might mention historical events, people, or trends, and you would feel out of the loop, like a very young child who misses whole portions of conversation.
You might even crave knowledge on this, wishing you could understand what is being discussed by the generation that lived through the actual events.
Consider that even before our formalized history schooling, people passed down information from generation to generation orally. Why would they do this?
Practical reasons include the need to understand how to survive and function in the world.
Our modern reasons go beyond this, but still relate to this desire to use the past accumulated knowledge and experience of human beings to better our own situation and prevent repeating mistakes made in the past.
Perhaps one of the most important reasons to study history is to spark interest to learn even more about these areas. It may seem as though history "happened" and now we learn about it, but our entire understanding of history changes over time. What we "knew" about World War II, for instance, changed when certain records were declassified and available to the public many years later.
We use different textbooks than we did 50 years ago or even 15 years ago. This is not simply because there is more to add to history textbooks as time passes, but also because historians gain a deeper understanding of the nature of past events and this makes its way into the way we teach these topics.
This can even be controversial! Who gets to write history lessons, and how does that influence what stories are told, and what stories are left out? Studying history well means we stay conscious of our own bias and the bias of those writing and teaching history.
Those who study history as professionals have this exciting task of examining the accepted assumptions about history and considering the evidence behind these ideas. Are they facts? Do we need more information? Where can we find that information so we can unlock more secrets of the past?
As another poster has said, one of the most significant reasons to learn history is simply to grasp our current state of affairs, and that of people all over the world. If we don't know anything about our history or that of other countries, we will have no clue of how to respond to conflicts, maintain relationships, or even plan for the future of our society in the most basic ways.
The Roman philosopher Cicero said it best when he wrote “To be ignorant of what occurred before you were born is to remain forever a child.” From the time we are born we learn from experience, in some cases we learn what we should do, but more often what we should not do. So it is with our history, knowing whence we came is the only way to, as Confucious said, “define the future.” All people and all nations must have a firm foundation of historical knowledge. It provides for us the knowledge to make informed decisions about where we are going. For as Winston Churchill insisted “The farther backward you look, the farther forward you are likely to see.” Knowing our past makes us whole, gives us purpose, and makes us who we are. The light to the future is much brighter when it is powered by our knowledge of our past.
We study history so we can understand who we are as a people today and why we are this way. I believe it is irresponsible to move forward without understanding the past since the decisions of the past the decisions of the future.
A second reason to study history is to just be awed by the people of the past and their ingenuity. For example the beauty and complexity of the Mayan civilization or the Early Grecian society should inspire people. These great societies so different and distant both created beautiful architecture thats has lasted thousands of years.
We study history to learn the essence of what happened in the past.