I think the Journey is often overlooked, when presented only with the result, sketches really show you what the artist is trying. It helps to see and motivate my own efforts. Not to mention all those lines are COOOOL
I'm a little middle of the road, but at times it's nice to see something in stages... Some artists post a final and then a side-by-side smaller version showing various stages of completion. I do like to look at those.