Imagine an umbrella without a fabric covering — useless, exactly like a language stripped of its cloak of cultural and social milieu. The sociocultural background of a language (or language system) is multifaceted, woven in extremely intricate patterns and colors of race, religion, socioeconomic position, climate, history, and all of the other elements that make up a society.
This interwovenness implies that some varieties will be closer to each other in some ways and farther in others, which of course reflects the case in reality. Such similarities and differences are quite easy to represent in terms of this model. If we liken the umbrella covering (as seen from above) to a template for a simple pie graph, we can easily create patterns for any criterion by which we might want to describe, delineate or classify the varieties.