Why is it necessary, in a formal report, to include a section that gives the background of the situation or the history of the problem?

Formal reports usually have a section that gives a background or history of the problem, even if the current audience already knows the situation. This is because reports are filed and consulted years later, and though later audiences will probably not know the background, it may be crucial for understanding the options that are possible. The purpose of most reports is rarely to provide a history of the problem. Do not let the background section achieve undue length.