If we think of it as a matter of memorizing a long list of dates or the causes of events like the Civil War, its importance is harder to understand. If we think about history as a way of shaping how people understand themselves and the society in which they live, its importance becomes more obvious. How and why groups within society respond to these influences is what historians are interested in discovering. The answers to these questions are never straightforward, nor is there always just one correct interpretation. How historians look at the available information and piece it together affects the final interpretations they develop.
Slavery is a good example.
At one time a group of influential historians considered it an overall positive experience for the slaves who were introduced to Western civilization as a consequence of their enslavement. Other historians who years later reexamined slavery did not find it such a good thing. The difference between the two interpretations was a matter of perspective and of looking at the facts in new ways. What some historians saw based on their training and their life experiences varied greatly from what other historians saw based on their view of the world. It is because historians interpret facts and influence how people see themselves and their place in history that it is important for a wide variety of people to enter the history field.