With all the flamboyance of colour & effects available to the digital image-creator, why go to a more traditional "drawing" look? Well, there's a richness of line and form that functions very well in working out ideas and visualizing concepts without the full onset of a major image. Combined with that is the poetical lyricism of the traditional drawing mode which somehow is almost instilled into Western culture as the poetics of image making. Finally, there is something of the Zen, 'AHA ! in the faster investigative pieces.
The Graphic application of drawings -- as illustrations to prose, or imagery in-itself has always been extremely attractive. Certainly the illustrative works of Daumier are a big influence here. There's an honesty to the drawn image. It's a great way to investigate ideas.