Noise and grain are not necessarily bad. Architectural illustrators sometimes intentionally generate this texture for interesting, creative effects. For one thing, it can add to the mood of a rendering. Think of the kind of image you often see on jazz or rock album covers (remember those?). The photographers who create these images often go for as much noise and distortion as they can, because it seems to best suit the subject matter and environment.
Generally though, most people want a rendering with rich colors and sharp, smooth detail.