As a history teacher, and as someone who is very interested in history in general, there are many things I value about studying the events of the past. Let me discuss two of them.
First, I am very interested in understanding why things happen. I value the lessons that history can teach us about why certain types of events happen. I like to look at history to try to determine what caused events to happen. Since you have been asking about the Vietnam War, I will give an example from that conflict. I like to try to understand what sort of mindset led Americans to believe that the war was necessary and that it was possible for the US to win that war.
Second, I am interested in trying to understand what it was like to live at various times in the past. Here, I am not trying to look at the big lessons of history. Instead, I am trying to understand how people felt at times in the past. In other words, I am trying to put myself in their shoes so that I can understand them as human beings.
These are two things I value about studying past events.