A camera’s light meter looks at a scene and tries to render it as average reflectance or 18% reflectance), which is middle grey, a value considered right between pure black and pure white.
The term “black and white” is inexact because, really, there is only one pure black tone and only one pure white tone. But in digital images there are 253 shades of gray.
Black, being the darkest gray tone, is stripped of all light, while white is the lightest gray tone, exposed with too much light. In either case one really doesn’t see any detail, because it’s either too bright or there’s no light.
Many of the early photographic processes printed as shades of brown, from dark chocolate to light taupe, or were rendered in depths of rich blues, or even in shades of silver. These all come under the heading of “black-and-white”, serving to emphasize the beauty of an image rendered in but one tonal spectrum.