People don't really talk about it that much.
You certainly won't see it mentioned in glossy fashion magazines wherein advertisers don't want to upset the feminists by talking about the rampant problems within the fashion industry (sweatshops, child slavery, anorexia, bulimia, overemphasis on beauty, toxic chemicals in makeup, etc).
Regardless of what you've seen in films like Pretty Woman, being used for sex is not a love story. Its a heartbreaking, nerve wracking and depressing experience often coupled with drug addiction and an abusive relationship with one's pimp.
A more realistic film to watch would be the French film "Baise Moi"... except cut out the part where the two women go on a killing rampage.
In the fashion industry its different. The women are looking for easy money by being a fashion model and often fall into the partying and drugs crowd and due to their addiction need to find extra ways to make money.
French prostitution ring which was recently busted and caught Dominique Strauss-Kahn in the process.
It is really only a hop and a step from the catwalk to the escort industry and the sex workers industry. In France and other countries where prostitution is legal its really not that surprising.
Take Germany for example. The industry has become so rampant they have glossy websites like Escort Berlin which let men choose which woman they want to have sex with.
What you may notice about sites like Escort Service Berlin is that the women are mostly imported from other countries... this is because Berlin is one of the top destinations in the world for sex tourism and they have so many men looking to pay for sex that they can't keep up with the demand so they're bringing in foreign labour.
Male tourists and businessmen looking for a good time... not exactly what you think of when you think of German tourist brochures, is it?
Traveling to Berlin / Sightseeing in Berlin? Why not hire Berlin's most luxurious escort agency, the premier in adult entertainment in Germany. Luxury companionship is only a credit card away and unlike other countries, legal and generally accepted by the German public.
Sorry if I am getting off topic with the whole travel / tourism topic, but sex tourism is a big thing in the prostitution industry. Adult oriented travel destinations is big business whether you are visiting Southern Germany, Paris, New York, Hong Kong, Tokyo or Beijing...
You will note that such places are both epicentres for fashion and sex workers. I guess we can't really be that surprised.
In an industry where fashion models frequently snort cocaine and shoot heroin I guess we can't be too surprised by anything in the modeling industry.