The back is a vulnerable part of the body, you cannot see what or who is approaching. "Modesty" is a body extension to deter people from touching my body, lower back, and upper back. In particular, where pants and bras cut into flesh. Working in the restaurant industry, it is common for co-workers and customers to feel comfortable touching these areas. The sociological issue is the lack of respect, and the lower rank that blue collar jobs are associated with.