The rule in portraiture is the key of the clothing denotes the key of the background and the key of the lighting. This means for a subject dressed in white or pastel clothing a white background and high key lighting (few if any shadows, NOT overexposure) should be used. Conversely, a subject in dark clothing should be posed in front of a dark background and low key "moody" lighting can be used. In fashion photography a white background is used for nearly everything as it takes the art directors copy easier, plus if needed it is easy to drop in another background or a company logo.
One problem in portraiture with white and black backgrounds are they are boring which is why most professional portrait photographers use muslin or canvas backgrounds in greens, browns and blues. I own about 25 backgrounds in muslin and canvas in a wide variety of colors, plus seven photographic sets in my meduim and low key camera room, and an all white high key camera room with a curved floor to back wall (a cyclorama.)
Benji