It's more subtle than that. For any given technique used to illustrate a scene, you could come up with a means of automating it, and those means are employed by

It's more subtle than that. For any given technique used to illustrate a scene, you could come up with a means of automating it, and those means are employed by professional artists on the regular, from rulers to draw straight lines up through 3D modelling software. A lot of finished work will go between the sketchbook and the computer and then back again to iterate on technical elements like proportioning and perspective. But what you cannot automate is the design work that puts together each of those techniques. You have to decide: how much detail to add? What are the spatial relationships? What will my light values and colors communicate? What shapes and forms should be given emphasis? And then at the level of storytelling, all the considerations around plotting and characterization; the themes of the story and how scenes develop to express those themes, and how that translates into imagery and the physical description of a character. Working on commercial art today is much more about these kinds of conceptual distinctions than about the quality of traditional pen-to-paper drafting skills. If you know how to pull out those techniques through automation, you can still get a satisfying result. But getting the "eye" for knowing what is possible still needs training.