Read chapter 1 of Ragin, C. C. (1994) Constructing Social Research: The Unity and Diversity of Method, Pine Forge Press.
In the same way that the constructs of the social sciences are constructs of the second degree, that is "constructs of the constructs made by the actors on the social scene, whose behavior the social scientist has to observe and to explain in accordance with the procedural rules of his science" (Schutz, 1954) so too the constructs of systems development are constructs of the social actors involved in development, either directly or indirectly (e.g. developers, management, customers, critiques).
Both the research methods for gathering field data, data on customers or users, and the methods or interpreting data, that is data analysis and theory induction, are crucial tools for the business analyst, for the developing requirements, for understanding and interpreting how systems are used and how they can be further developed.
Qualitative research methods are therefore crucial tools for gathering requirements, for trying out designs and their implications 'in use', to reveal unintended uses or consequences arising from new systems (like the Cobra effect), or to suggest gaps that might be addressed.
Schutz, A. (1954) Concept and Theory Formation in the Social Sciences. The Journal of Philosopjhy, LI, 257-67.
Read the chapters and provide a thoughtful observation or question (post to the comments section below).