Probably the easiest, most comprehensive definition of cartography, it’s purpose, and the demand users have for it:
[…] essentially place colors, shapes and labels of certain analysis on top of a basemap. the design of these two items [Editor’s note: basemap and results of geo-spatial analysis] becomes critical. the basemap gives us context of things we already know. i can usually recognize political boundaries (like states and counties), man-made infrastructure (like roads and buildings) and physical features like streams and mountains. usually we have seen these so many times, we subconsciously know exactly where we are without having to really spend time on the map. for instance we know that washington dc is halfway between maine and florida, that the sierra nevada range is somewhat coincident w/ the california nevada border, and its relatively flat between denver and say eastern ohio (ok not really, but). the results are then placed on top of the base context and highlighted; the red color here shows a creeping fire, or lots of environmental issues in this area, or too much traffic on that route home. imagine if we had to read text descriptions of all these complicated issues. compare that with the last severe weather map you were looking at. the later gives the consumer instant knowledge of the issue.
In fact the whole article is an insight for geo-interested people. Written by feomike, it is about the GitHub functionality to easily place geojson format files on a map in the repos hosted at GitHub.