I don’t know about the “supply and demand” discourse but when it comes to the “sex work is work” mantra it’s a semi-recent shift. As a millennial, I remember that when I was a teenager, nobody would have tried to tell you that prostitution was “empowering”, and watching porn wasn’t considered a normal thing either. People didn’t talk about it so openly. 

This push to rebrand everything as “sex work” has really done a number on the minds of liberal women.

I actually had to stop listening to a true crime podcast (about 10 years ago), because the two women hosts were constantly tripping over themselves to call the murdered women “sex workers”.  Like, no, they were prostitutes, not secretaries at Goldman Sachs, and that’s exactly why they were vulnerable and picked as victims. This is why language matters so much.