I am a big fan of both history and maps. I have a B.A. in History.
The ancient world of Egypt, the Middle East, Greece, and Rome, and on up to the Renaissance fascinate me.
The map of Germany with over 1,000 different countries is just fascinating. At my university they had a big hardback map book with a multi-colored map of Germany in the middle ages, and it just fascinated me. My paperback Rand McNally Atlas of World History is a passable substitute for such high-end books of maps.
Just looking at all the colors delineating all the separate nations generates the seeds of ideas.
Whether one is using a campaign set in a historical period of the ancients, or medieval, or a western, or post apocalyptic, maps help set the tone and flavor. Do you need to share the map with players? If they are a post holocaust type setting, would they even know they are on a planet and would they recognize a continent or larger scale map for what it is? In other settings, will players be able to afford a map?
Even if the maps you draw are only to inform yourself as the DM, don’t you want to share your creation(s) with your players?
I don’t have many books of maps. A well-done map is a thing of beauty. I like all maps, real and imaginary.
I don’t have the skill I wish I did to make my own maps. My maps are just crude representations of things. Some are better than others. I really appreciate all the maps available for my use from the plethora of OSR map makers!