So in this example, art history is the serious major?
When it's a course taken as part of graphic design for marketing, it is. You can't sell unless you have studied how people successfully sold before. And you can't understand how to use color for design unless you've studied how masters of the past did it.
Remember, some of Alphonse Mucha's most striking pieces were ads...for bicycles, soap, all sorts of things. And he did them for reproduction on a limited color press. There's a lot to learn there!