And we don't expect someone working in the office of a record label to learn the guitar, so why do we want artists to learn SEO?
I don't mean SEO. Most artists aren't even taught the BASICS. How to keep track of their expenses, how to price their work, how to negotiate gallery and commission contracts. How to cultivate relationships for repeat customers...
And for all those artists who were taken advantage of (especially in the music industry) because they didn't understand the business side of their art/craft it is super important.
Every creative job (including the arts) has aspects that aren't directly related to "making art" but are still necessary.
You can always do art for art's sake, but in order to make it a "profitable" career, you have to do some of the side work or partner with people who can do it for/with you*. The more profitable you are, the easier that is.
FWIW - my background is in arts nonprofit management, with a side biz of coaching artists to become profitable. So, I have some very strong opinions on the matter, which is why I have stayed out of this thread thus far.
Edit: I really do love your personal definitions, Watchmaker.
Edit, Edit: Actionable tip: Several visual artists I know have been working the theory that connection with the artist is more important than the actual art. They have started putting their pictures and stories WITH the art, either as part of their artist's statements in galleries,or more often, in their online galleries and have seen sales triple. People are buying your passions, story, expression.