Various agri products that lead to preparation of food across the world tells you a lot about resources and economics. Infact, it tells you much more about economy than several economics text books put together. The European search in the 15th century was mainly to figure the magical spices to make their food edible and tastier. Even before Europeans came to Indian sub-continent and destroyed it eventually, there was active trading in rice and spices between India and Middle east and so on. It is the surplus generated from agriculture which was a major factor in other developments as well.
Thus, history of food tells us about available agricultural resources, constraints and so on. How certain dishes eventually come up as a result of these resources and constraints tells you about geography and so on (it is other way round as well). Then, some dishes go on to become popular across other regions whereas others remain local as the ingredients (read resources) may not be available and so on. For instance, the story of Haldiram Bhujiawala is one such story.
Sanchari Pal has done a good job explaining history of idli/sambhar and that of dal/baati and littis. In Idlis, availability of water was not really an issue whereas baatis and littis emerged due to shortage of water.