There is information that is not very important to explain in your report but it can help to pursue or conclude a related point in the report. Such pieces of information should be placed in the appendix .
An appendix may contain long information, graphs, tables and repetitive sentences. It also helps readers to judge the quality of the report data sometimes a small excerpt is used in the text and is elaborated in the appendix.
Therefore, the appendix should be used frequently in the reports to not only improve its quality but to help readers to process dense information.