Sketching for 2D work is perhaps less common now, but hardly a dead (or even dying) art. Probably most practitioners come from the old school, but plenty of younger designers still whip out the pad and pen.
Just got this book, one of several on the subject:
http://www.amazon.com/gp/product/1592535216/ref=ox_ya_oh_product
(“Sketch Book: Conceptual Drawings from the World’s Most Influential Designers” Timothy O’Donnell)
Full of incredible work and some great descriptions of process and projects.
c.