I know inking a drawing is important for many pieces, but I was wondering what, in technical terms, it does to the image. I don't mean "it makes the lines thicker," I mean more along the lines of, "It makes the image clearer" or something like that.

I ask because for a long time I felt (and still feel) that my sketches lacked life, lacked a certain crispness, but when I went over them a second time and bolded the lines, they seemed to find that life. Is inking truly that important in giving life or clarity to an image? My gut says yes, but then I visit the CC or GB and see very light sketches that still manage to look very vibrant and clear. What gives?