In the game industry and elsewhere, there is a position called "concept artist". The job responsibility for a concept artist is to communicate to the development team what the game will look like. It is a simple task to define, but there are few people who excel at it. Even worse, most people who are hiring or working with concept artists don't really understand what makes good concept art.
The root of this problem is that most people do not understand the difference between a piece of concept art and an illustration. Yes, they are both static, graphic depictions of something. But the difference in intent could not be larger.
An illustration is an end in itself. It is meant to be presented directly to the final audience. The audience is meant to see an illustration, and come away with a certain feeling or understanding of a visual event. This directly implies a hard division between what is and is not important in illustrative work.
It is important that an illustration be attractive. It must use color and shading in a way that evokes the desired response in the audience. It should been constructed so that line weight and spatial contrast work to convey certain feelings about the different portions of the drawing.
It is not important for an illustration to be complete beyond what is seen. Could the room in the drawing really be part of a larger building? Could the characters really be standing where they're standing? Would perspective really make them look like that? Are those straight lines really straight, or the curved lines really curved?
All these questions are irrelevant. As long as the drawing produces the intended effect in the audience, the illustration has done its job.
The final audience is never going to see a piece of concept art. They are only going to see the result of the communcation between the concept art and the development team. As a result, the importance of each element is precisely reversed from its importance in illustration.
Concept art is not supposed to look good. That's not the point. It doesn't need to be shaded, it doesn't need to be emotionally involving. What it needs to do is unambiguously communicate the form and intent of the concept. That's why it's called concept art.
The (talented) concept artist has a coherent vision of what the world and characters will look like, and the concept art needs do nothing more than embody that. The concept art will be handed to modelers, animators, and texture artists. They are the people that need to make it look polished and attractive, because they are working on the art the final audience actually sees.
Thus for concept art it is much more important that all of the structure be sound and not an accident of the drawing. All buildings should be solid, spatially correct, physically sound. Lines should make sense, and be directly constructable in 3D. Nothing should be exaggerated, intentionally distorted or misplaced in any way that only makes sense from one view. Characters cannot be constructed to "look cool" in a particular pose when there are obvious dire ramifications of building such a character in fully animated 3D.
This is perhaps the biggest single common difference between good concept art and good illustrative art: view-dependence. A good artistic illustration often could not exist in reality because some aspect of it has been contrived to make the particular view more exciting. It often does not show aspects of the characters or environment that are not pertinent. Concept art is the opposite. It should always be able to exist in reality exactly as drawn, and all aspects of the characters and environment should have been thoroughly explored and drawn.
So now we come to the crucial problem, which is that most people (often including the concept artists themselves) do not realize this distinction. At hiring time, people look at portfolios and judge them based on their quality as illustrations. They judge the art as if it was for a finished product. Why? Immediately after you hire this person and put them to work, they will never again produce a finished product. They will be working only with concepts and communicating those concepts.
This needs to change. People need to learn how to look at a work and judge it as an illustration or a piece of concept art, depending on the situation. They need to realize that a good illustrator may be a bad concept artist, and a great concept artist may never do good illustrations.
The sooner the better.