It may explain the methodology of the studies it cites.
Simply citing the answers from various studies may not not enough. While a study may prove that X has a correlation with Y, a study's methodology is important - especially when it comes to social sciences, where different definition of terms like "happiness" or generosity" would change the answer drastically.
Knowing the methodology, then, may be important to helping the reader to assess how the study may be relevant to the question.
