The problem is that the set of things that are illegal in some country at this particular time, and the set of things that are "rationally definitely wrong everywhere, for all time" are never quite overlapping perfectly.

Sex slavery? Arguably rationally wrong for all time and space.

Drugs and prostitution? Debatable.

For example, regulating drugs and treating addiction as a medical problem is probably much cheaper than waging an unwinnable drug war PLUS trying to find all the laundered money coming from it PLUS forcing all the "good actors" (non drug industry people) to comply with the regulations at no trivial expense.

This is true for every economy that refuses to go away despite being wholly illegal. In those cases it is (IMHO) best to just regulate it... Same as what happened with alcohol after Prohibition. Nobody's making moonshine and killing bootlegger opponents anymore, and alcoholism is a manageable medical problem.