When reading works like this one I tend to find three stories being merged into one. It focuses on slavery where most of the evil aspects of humans tend to come out, as in order to reduce a human person into something that can be traded, everything that gives that person a social context must be torn down. This is where the "break down" period comes from and it's a common theme in everything from the African slave trade to forced labor camps. Slaves are broken down, displaced, and controlled in order to place them outside the social economics shared by everyone else.

The second story is one about social stigma. We live in a society which views sex trade to be worse than going into a life of crime. From a social standpoint, it means that providing a sexual service in return for money is worse than breaking the law and social order that society is built on.

The third, although one which often is used as an introduction, is one about poverty. In order to get food on the table people will agree to many kinds of dangerous, dirty, and unwanted lines of work. People have entered the death sentence called a coal mine, gone into work which has a life expectancy of months, but in contrast to prostitution those are often viewed as sacrifices rather than something shameful. I suspect this has something to do with gender roles, where a man who is forced by poverty to unwanted work is a hero while a woman doing the same is a victim.