Look at pot, for example. It’s legal in many states and that has generated new business models and products, including lots of CBD products. In my life, I’ve never been interested at all in smoking anything. But I’ve used some legal CBD products. Because they are legal. The market has expanded.
But you never crossed your original line: no smoking.
And I do agree that legalization does tend to expand markets--but note what happened here. New
low end options showed up that were not particularly viable in the illegal marketplace as illegal markets reward potency. Yes, some people partake that would not have otherwise, but in the other direction some people step down to the less potent options when given the opportunity.
Ever notice that one coffee shop on a nice corner often leads to another coffee shop? Same thing with fast food and tattoo parlors.
Availability generates demand.
As your evidence for the arrow of causality is???
No, demand generates providers. Providers do not like competition--Starbucks puts a clause in their leases prohibiting other coffee shops in the complex.
Do we think that making pot legal has increased or decreased demand for pot? Has it had an impact on illegal drugs? Would legalizing drugs reduce demand or increase it? Reduce the negative consequences of drug use? Sure, it would reduce arrests for buying/selling/possession. I applauded d that! But there are plenty of other negative effects.
History gives us a few examples:
1) England used to take the addiction is a valid reason for a prescription approach to opiates. Result: very low rate of opiate addiction because there were no dealers. (And note that a substantial chunk of our fentanyl problem comes directly from the drug war. The problem was Oxycontin often did not perform as advertised and the DEA was obsessive enough about prescribing practices that the doctors weren't at liberty to prescribe what the patient actually needed, thus driving a lot of people to the street.)
2) Some places have taken decriminalization approaches. Nowhere near as good as legalization (there's still all the negatives of the illegal supply chain), but it doesn't increase addiction rates.
Legalization would do nothing to reduce the demand for underaged sex workers. It would not reduce the demand for what could still remain illegal. It would not guarantee that sex workers are willing participants but it would make it easier to claim that they were.
You're assuming there's much demand for them in the first place. And why do you think it would make it easier for people to claim prostitutes were consenting? Make them take their license exam (yes, there should be one--safety practices) alone, do a bit of an interview. That would screen out most of the coerced ones. Make the licenses anonymous--picture but they can put whatever name they want on them. Put a 2D barcode on them, if scanned it pops up the picture and license status. They can remain anonymous while permitting verification. And you punish anyone who patronizes a prostitute without a license.