Why were Delhi, Paris, and Washington, D.C., examples of cities with orthogenetic roles?

In the study of urban culture, sociologists Robert Redfield and Milton Singer identified cities as having varying cultural roles. They classified Delhi, Paris, and Washington, D.C., as examples of cities with orthogenetic roles because their primary function is the construction, elaboration, and safeguarding of a society's traditions.1

In these urban centers, cadres of literati work to rationalize and codify a "Great Tradition" for the society at large. As capitals of classic empires or modern nation-states, these cities serve as the cultural heart where established traditions are maintained and transmitted to the wider culture beyond the urban precincts. This role contrasts with "heterogenetic" cities, which act as centers of technical and economic change, introducing new ideas and social practices.1