Don't take that as I purchase those services because I don't nor do I ever plan to- not really my thing. But some people always will, after all it is the world's oldest profession.
You are absolutly right, but the same can be said for every crime. That isnt a good argument, saying nobody is directly put in danger by prostitution, or that it doesn't breach the peace is the argument to have.
The statement above says the law isnt 100% effective so lets get rid of it, that is not a rational argument.