Bar charts also involve comparing objects on a common scale, typically the x-axis, but Cleveland and McGill admit they can also involve judgments of length and area. The list goes on. I encourage you to read and familiarize yourself with what they consider to be elementary perceptual tasks.
It’s perhaps a science because it must represent data accurately, methodically and without flourish so that we can see the underlying trends and patterns. Because of this, selecting the right visualization for your content could be prescriptive based on what you want to show.
It doesn’t provide geographical information: The map of cancer rates doesn’t provide a spatial pattern. Things look kind of randomly or haphazardly distributed around the state. For that reason, showing the data on a map isn’t a strategic improvement over showing the data in a chart.