Not really any reason for them to do that. The studies and documentaries are put together by social workers. At the lower levels, these people have an intrinsic need to feel superior to the people they study and "help". They mean well, but they are a hassle. Most of them are honestly not too bright (it is an easy subject in school and the only career avenue for many of those that were themselves "helped" or "saved" from bad circumstances). At the higher levels, the people that run businesses and government agencies focusing on social work rely on funding and grants. By relying on the most extreme examples, they are able to maximize funding opportunities. With respect to the media outlets for the stories, they survive on advertising revenue. Stories that appeal to gullible people who like confirmation of the stereotypes they have always been taught will generate more successful advertising. Dumb, gullible folks buy what is advertised, and business caters to them. A major US pharmacy chain now has an "As Advertised on TV" section. God help us.
There have been a couple of studies of the higher-end US prostitution market. The University of Chicago economics professors who wrote Freakonomics dedicated a chapter to a lady who was an independent escort who gradually was able to increase her rates. She is sometimes a guest speaker at their classes. The professors express bewilderment that more women do not do "upper-level" sex work. They compared her life to that of a streetwalker and demonstrated the differences. It is a fascinating study, and says a lot about poverty in the United States. The obvious conclusion that I gathered is that the best approach to increasing the incomes and happiness of sex workers is for them to become better sex workers.
Of course economics by its very nature will never produce any great solutions. If a person reads the comments and reviews on theeroticreview and on usasexguide.info, he or she will see that the johns paying $350-$600 U.S. are different than the ones paying $100-$250 per hour in the United States, and the providers are very different. I am sure if you divide those numbers in half, the principle is the same in Montreal. But the U.S. media only focuses on the low-end of the market, and that creates a danger to the high-end if laws and law enforcement treats everyone the same, partially as a result of propaganda.