To a large degree, it is not vitally important that historians research the past, and particularly not some parts of the past. The practical point of historical research is to help us understand the choices we have as we face our own problems today. Much historical research is not particularly useful in that regard. However, we can argue that researching the past is important (to some extent) in two ways.
Historical research is important simply because we people want to know things. Human beings are endlessly curious and historical research helps us “scratch that itch.” For example, there can be no real importance in knowing exactly where the city of Troy was, but people just want to know. Things that have practical applications are not the only important things in our lives. History is important in part simply because humans want to know things.
Historical research also has practical implications. It helps us understand what human beings are like and what mistakes we tend to make. This can help us understand our present situation. For example, let us say that historical research tells us that environmental problems caused the fall of various ancient civilizations. That might imply that we need to be more careful about what we do to our own environment.
Thus, historical research is at least somewhat important both for practical reasons and for reasons that do not have practical applications.