We are all alike and we are all different. Average is but a thin strip of the range. Chaos theory does not dictate a method but, recognizes both commonality and variation, along with their possible subtleties, as important factors when considering a phenomenon. At the real-life level, purpose dictates method or approach. Just as society contains individual, city, state, and culture so to theory addresses many issues.
Theory performs the same function as culture.
It is a reference point. The reason we need theory or theories is so that we know and understand the point of view from which research is born. This encourages critical focus on the questions or assumptions, and enables objectification of subjective findings. But as always, question determines method determines findings. The most defining, confining and beneficial aspect of theory is that it forms a common vocabulary and directive which exposes the context within which the research exist.