Thanks Derek. Exploring the intersection of what we might think of as traditional-cartography with GIS mapping is the current working topic for my masters thesis... so I've given it some thought.
There are some really important benefits to cartographic design in analytical mapping but that notion of art seems to be an obstacle to many practitioners. The real problem for many people making maps with GIS is their final purpose is often ill defined, by themselves or their mentors. They may think that they are only interested in exploring the data to answer a particular question but at some point in most GIS projects there is an output: to other researchers, to administrators, to the public, to potential financiers... at some point communication becomes the most important aspect of the project. And effective visual communication is tied directly to effective visual design. The need to design is inherent in almost any map project involving GIS but it currently gets little to no attention in GIS training. As a response to this many crutches have been developed to help aid the untrained in making better cartographic decisions (the "Brewers" etc.), but the best work is still going to come from those who get that design is related to information quality and not just appearance. I see a big interest in the GIS field as a whole for more training in real map design but still a lagging response from the educators and institutions.
Again, great post, David!
I agree with that bolded sentiment in particular. I think what it boils down to is that many in the field have little to no idea about marketing. They'll spend 100 hours making some map of 14th Century ___________ that is of interest to them and about 1,000 other people on the planet (who they don't know, and cannot easily locate), then lament about why they've only sold four copies of that great map in a year...netting them about $0.50/hour for their effort.
Sales? That's part of marketing, and anyone here who makes maps for a living who is still alive (hasn't starved to death) knows a little something about sales by now.

But sales is one small branch (a very important branch) of marketing.
What about the idea of market research, as one of many other examples? Knowing one's competitors? Knowing one's end-user base and what they truly want/need (and what they are willing to, or can afford to, pay)? Knowing the difference between a "champion" of your services and the person who has the decision-making authority and purchasing power? Knowing how to properly track campaigns and use analytics? Knowing how to DEVELOP campaigns and position one's products and services in such a manner as to maximize earnings potential, minimize direct competition, legally build/avoid competitive barriers to entry, et al?
During my undergraduate course work in graphic design, all we were ever "taught" about marketing was
"if you're good at what you do, people will want to hire you." AKA if you build it (well), they will come. But being good at what you do is just one
tiny part of earning a good living. You've got to have a more memorable image/brand. You've got to be positioned properly so as to focus a majority of your time/attention selling to the folks who are most likely to consume your products and services. You need to maximize your per-hour ROI...especially since so many of us here are one-person shops trying to do everything by ourselves! Particularly when it comes to not chasing a lot of leads that have a low probability of turning into $$$ (or wasting time on prospective clients who either want to pay you minimum wage for your work, which drags our entire industry down every time any of us agree to work for "slave wages," or where you'll net minimum wage after responding to their 50-page RFPs and completing a few dozen of their TPS reports).
Marketing (including sales, but not "just" sales) is an art...every-bit as much as creating illustrations might be. But I fear that much of the "art" of marketing has been drown out by the "science" of marketing for a lot of folks...just as the "art" of map-making is being drown out by the "science" of map-making the past few decades.