There was a time when economists were inevitably concerned with development. Early economists of the 16th and 17th centuries to those of the mid 20th century were all essentially concerned with understanding the processes of economic growth and structural change: how and why they occurred, what forms they took, what prevented or constrained them, and to what extent they actually led to greater material prosperity and more general human progress. And it was this broader set of “macro” questions which in turn defined both their focus and their approach to more specific issues relating to the functioning of capitalist economies.
It is true that the marginalist revolution of the late 19th century led economists away from these larger evolutionary questions towards particularist investigations into the current, sans history. Nevertheless it might be fair to say that trying to understand the processes of growth and development have remained the basic motivating forces for the study of economics. To that extent, it would be misleading to treat it even as a branch of the subject, since the questions raised touch at the core of the discipline itself.