There's a reason for this, in that both sports seasons and military campaigns provide a narrative of events with a beginning, middle and end. This is not exactly true of history in its more general sense, except where biography is the template. Yet my friend, a trained historian, has identified something that I am not sure has ever been studied, which is the institutionalization of the concept of "the fundamentals". Early professional baseball managers and captains made things up as they went along, whereas today's managers pretty much have a framework through which players move and arrive knowing what is expected of them in a major-league game. The process by which that institutionalization arose is not well studied.
The kind of program described in this outline of a Spanish digital journal, Military History, suggests that academic military history could easily avoid its endangered status by casting its net wider:
Military History Digital Journal is an interdisciplinary journal, created by a group of history scholars and scholars in other disciplines. Our interests are diverse, and not simply restricted to the conventional study of history; we also explore the portrayal of war through the media of art, cinema and literature. Our field of interest is wide-ranging, and does not focus on any particular historical age. Research papers on terrorism, civil-military relations, military thought, warfare and technology, and politics during conflict are equally embraced.
Hat-tip to ubiwar.com.