But it doesn't actually matter why. It's a known fact that sex trafficking still flourishes in nations where prostitution is legal, despite your insisting it magically goes away. In fact, the evidence shows that sex trafficking actually increases as a result of legalization.
No, that fails for the same reason the prohibition analogy fails. The supply of marijuana and alcohol can easily be increased to meet increased demand by simply planting more pot or distilling more booze.
The supply in prostitution is fundamentally different. Women willing to sell sex don't grow on trees. You can't just build another prostitute factory. If the demand for sex (men willing to buy) is larger than the supply for it (women willing to sell), there will be a black market for sex.
Meh. You are laboring under the sordid and dirty practice of the illegal sex trade of yesterday. No one is suggesting a continuation of status quo with legalization. You are warped by stigma. You cant or wont see what a legal prostitution business could be. Regardless...the laws today dont help. At all.