I don't think laws from the sixteenth century count as modern. *Actual* modern prostitution laws are puritanical horseshit nonsense that have nothing to do with concern over the spread of diseases and everything to do with people worrying too much about what other people do with their genitals.
I think BD said originated in, not were still as. They were a result of puritan reform but there was a public health element as well. Prostitution was legally protected in much of Europe until the 16th Century. The 16th Century was a volatile period in many ways, religious morality being one.
As for modern laws having
nothing to do with the spread of disease I think that's superficial. Neither are they
entirely about concern over the activities of people's genitalia. There
are issues around prostitution that when taken at face value have little or nothing to do with health or puritanical nonsense but everything to do with what's right and wrong; the growth of sex tourism being one and human trafficing another - both involve prostitution, albeit often involuntary. Sex tourism has a rather fuzzy illegality to me, until it involves minors and/or coercion.
I think prostitution should be legal, if for no other reason that I don't believe the state should have a right to dictate what any consenting adult does with their body whether for financial gain or not provided no other crime is committed and no harm is done.
As for Porn movies constituting prostitution by proxy, I suppose one could see it that way. I'd lay odds catching some form of disease from a porno house wasn't outside the realm of possibilty.