You can pick out a skilled painter or draftsman because they keep their eyes on the canvas or paper without having to constantly check every line they draw by comparing it to the model or original image, or having to look up, again and again, pictures of what they have to draw on google images. They trust their instincts and skill, and their lines are precise, and they have developed the necessary muscle memory that allows them to be skillful artists.
All the arts have that, a combination of skill, knowledge, and automatism that baffles the uninitiated. It’s mostly years of experience and practice. Well, I said all the arts, except writing apparently. There doesn’t seem to be a writing equivalent for that process of learning the fundamentals that other arts have, like painting has color, tone, and values, while draftsmanship is mostly line, shadow, and perspective.