Why would a researcher use a primary source instead of a secondary source when analyzing a historical event?

As primary sources provide firsthand views or evidence regarding the situation, they are more relevant and convenient to use than secondary sources. Primary sources regarding a historical event could possibly relate to eye witness accounts, relevant documents, and certain types of statistical data. Secondary sources however, may not provide the correct information relevant to the situation as they discuss or present information that is originally presented elsewhere. Examples would be review articles of the event instead of the original data.