I've always been confused by that too, how does a camera being there change anything? Objectively, selling yourself and being filmed sounds strictly worse from the no prostitution point of view.

First amendment. It mostly comes down to obscenity, not prostitution.

Also People v Freeman, which makes the distinction that porn merely pretends to be prostitution, because whats actually going on is a business venture to produce a media product that just happens to include hardcore sex and the performers are paid.

Communicable diseases.