Why is remaining objective important to the studies of history?

One challenge faced by all historians is remaining objective in their research and studies. This requires us to look at information for what it is, not what we want it to be. It also means considering information in its own historical context, rather than through the lens of our own modern age. Why is this important to the studies of history? Please use the book- A Concise Survey of Western Civilization : Supremacies and Diversities Throughout History by Pavlac, Brian Alexander and cite chapters 1-3.