When I was in school taking art every day my requirements included a drawing every day. OK, so more than a few times I ripped through five or six drawings just before deadline (You know, that A.D.D. thing.) But in total, this drawing every day was a very good discipline and, in fact, necessary to developing the skills needed to become excellent. "Is drawing important?" Students actually ask that question, or worse still, "I don't want to worry about drawing, I want to paint".
If I could recommend any one thing necessary to be an effective artist it would be the development of drawing skills. In my opinion it is not just helpful, it is essential to become a competent draftsman before one advances into color. Just as arithmetic comes before algebra, drawing is the foundation for all things art. Let me define my terms. Drawing: artwork done absent color. This includes pencil, charcoal, and ink. Notice that ink is a wet medium. Painting: Two dimensional artwork in color. Oil, watercolor, pastel, collage, egg tempera, etc. Pastel is often mistakenly grouped in the graphics section of a juried exhibit, but comprised of pure pigment, pastel is the most direct form of painting there is. (Pigment in a stick, with just enough water to hold its shape. Pure color.)
I don't think of drawing as linear; that would be a coloring book. Outlines, even lines, are not found in nature, and a drawing can exist completely absent line of any kind. The idea that drawing is outline and nothing else is one of the most pervasive beliefs my students have. Not true. Taken to photographic detail, a drawing, like a black and white photo, does not need any line at all. Even a telephone line or a fence wire is not a line, it is a thin cylinder with light and dark shadows.
Line should be a beautiful, varied descriptive addition to your drawing. It can be first, a way to place and plan your drawing, or second, a descriptive lyrical element to finish an edge just so. A drawing might even be developed with line alone -- a beautiful elegant contour line or an expressive, active gesture. In any case, think of line as a beautiful, expressive element of the drawing. Outlines belong to the world of coloring books. (Do coloring books influence our children's understanding of what a drawing is and how it is made? Another time...).
Drawing is the description of form, defined by light and shadow. My own drawing is informed by the belief that the process is exactly like painting in its major components of design, concept, and technical application. In other words, I think of drawing in terms of seeing shapes; the shape of light, the shape of shadow, and the shape of the negative around or behind the form itself. Personally, I tend to work from the inside out, describing an entire shadow shape as a massed area just as I would block in the shadow areas first in an oil painting. This method has developed over time, with more and more of my ability to see the shape of a shadow as one continuous shape, rather than the edges of "things" or objects as separate entities. This is not my own discovery, though I remember when I first understood it as a life changing event. If you read any good book on painting or drawing you will hear this same thing, but expressed in many different ways. From the general to the specific, massing general shapes, first the dog, then the fleas – all say the same.