At very high ISO values, noise tends to intrude. Moreover the conditions under which such high ISO values are required often involve very difficult lighting. Hence, a black and white rendition can be relevant and useful, practically speaking, at least for eliminating unpleasant color casts.
In this example the lighting is excellent, so color casts are not the issue, but the black and the renderings at each ISO value give an idea of the subjective noise quality.
Includes image sizes up to full resolution.
Shot with the Zeiss Milvus 85mm f/1.4.