https://mises.org/wire/catholic-theologians-prostitution-should-be-legal-0
> [Aquinas] notes that the state should allow fornication and prostitution to exist for the sake of the common good. Relying on the well-known passage from Augustine’s De ordine, Aquinas advocates tolerance of prostitution by noting: “Accordingly in human government also, those who are in authority rightly tolerate certain evils, lest certain goods be lost, or certain evils be incurred: thus Augustine says [De ordine 2.4]: ‘If you do away with harlots, the world will be convulsed with lust.’” If these social practices were to be suppressed, the public reaction might be such as to threaten the peace of society.
plus with ivorce stats and the state of the economy it can be hard to afford a family, etc.