Why? I enjoy drawing with various approaches and materials, including graphite pencil, ink, colored pencil, different pens, and pastels. For example, even when just sitting in a chair and looking out at a landscape or at the nearby items in the area where I'm seated can have surprising results. I will often leave the drawing in black-and-white line form, and other times I'll use colored pencils, another favorite material, to add the aspect of color. This is really how I work in general - but in drawings it's linear and in black-and-white for the most part, at least until--if or when--I decide to add color. This might happen by colored pencil, markers, even sometimes digital color work will be a part of this process. I really also enjoy the ways this experience is so different from pastel or painting or even monotype, which to me even when there is linear detail usually has a more of a color-field quality. Doing these line drawings is way of reflecting and looking at the subject that is often opposite to my other methods, even if the 'subject' is one that is more "interior" and not a landscape, scene, a person, or something else outside of myself.
Another approach I use that is fascinating is just putting pencil to paper and, in a sort of meditative state, allowing the pencil to wander on the page. In this process I do make "decisions" but it's more in a way of observing where my hand takes the pencil...or perhaps where the pencil, or other tool, takes my hand.