More attention is paid to the volume of the forms and the lighting with this technique as opposed to the contour of the drawings.

There's often more opportunity to create value relationships with rendered Black & White frames than the quicker sketch based on more linework.

I've often said that it's not necessarily an easier problem to solve, a frame devoid of color. In my opinion, as an artist, you have one less weapon in your arsenal to create a great image. That said, a powerful frame executed in grayscale values alone can be even more impactful than a color frame at times.