Most obviously, it forces students to recognise that major discontinuities in economic performance and economic policy regimes have occurred many times in the past, and may therefore occur again in the future. These discontinuities have often coincided with economic and financial crises, which therefore cannot be assumed away as theoretically impossible. A historical training would immunise students from the complacency that characterised the “Great Moderation”. Zoom out, and that swan may not seem so black after all.
As Robert Solow points out, “the proper choice of a model depends on the institutional context” (Solow 1985, p. 329), and this is also true of the proper choice of policies. Furthermore, the 'right' institution may itself depend on context. History is replete with examples of institutions which developed to solve the problems of one era, but which later became problems in their own right.
Doing economic history forces students to add to the technical rigor of their programs an extra dimension of rigor: asking whether their explanations for historical events actually fit the facts or not. Which emphatically does not mean cherry-picking selected facts that fit your thesis and ignoring all the ones that don't: the world is a complicated place, and economists should be trained to recognise this. An exposure to economic history leads to an empirical frame of mind, and a willingness to admit that one’s particular theoretical framework may not always work in explaining the real world. These are essential mental habits for young economists wishing to apply their skills in the work environment, and, one hopes, in academia as well.
[…]economic history is a rich source of informal theorising about the real world, which can help motivate more formal theoretical work later on.