To sell it in the first place. Screenshots sell games.
Good graphics are a big part of what sell games today, theyre not the only thing to think about. Gameplay is much more a factor then graphics, but you have to mind both. (I think a good example of a bad balance would by Xylvan's candy/light whatever world stuff. He spent way to much on graphics, not to mention over-blooming, instead of actual polish and gameplay)