As the old adage goes "those who forgot the past are doomed to repeat it." Studying history not only helps us to recall the events that have passed before us, but it gives us great insight into humanity at large. There are many reasons to study the past, and I'll outline a few here.
First, the past has shaped our present. An understanding of, say, the political tensions of the Cold War is actually very pertinent today, with countries like North Korea and China beginning to create nuclear weapons and Russia being accused of spying and political interference.
Second, history does tend to repeat itself, in a broad sense. By seeing the trends and events that have happened in the past, we can predict what sort of things may happen in the future.
Finally, history gives an understanding of human nature. Historical events and the responses people have had to them give an incredible insight into the human condition and informs psychology, sociology, and much more.