is simply that, from a law enforcement stand point, you can't enforce this stuff at all. Some place like Nevada's sex ranches, you can check IDs, of both the people working, and the people coming in. You can't even legally acknowledge the ones running the "street" based rings, verify ages, other than arresting them, prevent the pimp from bailing them out, then selling them off to someone else, so they never show up in court, etc. You hardly need a business license for it, never mind a physical place of business. If "any" of those things where needed, or possible, you would have far fewer people breaking the rules, since it would be more expensive to break them than run a legit business.
But it doesn't just stop there. Unless you plan to use reversible forms of chemical castration, on both men and women, until they get into a serious "relationship", or plan to police those relationships to prevent people ever cheating, never mind that the definition of the later can get sloppy, in that you have swingers, or even people hiring for one time three ways, or the like... Basically, way more than even drugs, for which much of our problem is the politics that its cheaper and easier, in the short term to jail people, and make big busts, than it is to find *real* cures for addiction (which, in the case of ones like one being tested in Europe, can be almost as dangerous as the drugs they cure), and programs that can try to find other solutions for people, than taking drugs (which would have to start with the near universal use of things like steroids in sports, etc., or if you can't/won't fix that, then better availability of "safer" ones, which don't promote worse usage), you can't **cure** sex. People are going to want it, people are going to do it in anger at a boy friend of girl friend, people are going to do it to see what its like in a group, etc., etc., etc. And, the whole system is 100% stacked *against* dealing with human trafficking, and child porn, because you can't tie the ones that "would be" legit, if they could, down to a known location, and the rest, don't have a permanent address, so instead of dealing with a small number of people doing this, you.. well, you end up doing the equivalent, in the "drug war" of watching 4 meth manufacturers change neighborhoods, due to being spooked, while busting two idiots in a car, for 4 ounces of pot.
But, that isn't the worst problem. The semi-normal activities are so prevalent, and so impossible to keep track of, that probably 70-80% of the police departments in the US deny, don't believe in, or don't want to hear about, "human trafficking". Maybe that has changed in recent years, but no near total denial of a problem *ever* changes over night, and most of them **still** treat the people they arrest as having "wanting" to be in the business, or "wanting" to be drugged, or "wanting" to be bailed out by someone, and ending up back on the street.
How do you prevent trafficking, if the police departments assume that every person they pick up is either a) there by choice, b) a run away, or c) wants to go back to their pimp? And, how do you tell which ones *are* in the above three categories, if the **only** people running such businesses are doing so illegally, and its therefor impossible to tell a) who chose the profession, b) who actually got the job as a runaway, instead of a kidnapping, and c) whether of not the person bailing them out is, the pimp, a representative of the pimp, or their kidnapper?
If you don't fix the basic problem, the fact that places like Craig's List have postings that are of questionable content is as meaningless as accusing Ebay of sometimes having things posted for sale by people that stole them. Its meaningless, and removing it entirely only, as you say, engenders the creation of someone else to do the job, and undermines businesses that provide more legitimate (albeit, indirect, and therefor the police can't arrest you for it..) business. And, that is also a huge joke. Its like selling someone an "herbal" supplement, instead of a "cure for baldness". You can be arrested for the later, but not the former, even if it is the *same* product, and even if you say, on the box, "may cure baldness". You can be arrested for "selling sex", but not for, "selling escort services". Shear idiocy!!!