Even if our hands are quite clean, we wash them before eating rather than after, like a cat. We prefer to serve food in dishes on a tablecloth rather than straight out of the can, although the physical, nutritional qualities have not been enhanced. We even say a grace or a benediction. After encountering an attractive potential partner, people do not proceed directly to physical intimacy. The more physical the activity, the more awkwardness and subconscious embarrassment surround it.
Nudism is practiced with a certain bravado in order to conceal the underlying tension.
Famous photographer Richard Avedon shattered a barrier by capturing images of people as they ate. Frozen in the act of chewing, humans resemble apes rather than angels. Our mothers, themselves raised in America's Judeo-Christian tradition, taught us never to eat in public. Similarly, we express a normal and healthy reticence about bathroom activities. On the other hand, as purely spiritual occupations, reading and art evoke no discomfort.