Isidingo - The Need

Why is it that in even the most modern of cities, prostitution is still taboo?
Now please, don't get me wrong here. I'm not talking about child prostitution. I'm not talking about human trafficking. I'm talking about a business transaction between two consenting adults.
Why is it wrong? Why do governments feel they have a right to get involved in something like this? Who does it harm?
Don't give me the nonsense that it "harms family life".
The family life is already harmed if a man goes to a prostitute if that is not part of their mutual agreement. The act of going is not causing the harm.
Don't tell me about AIDS and STDs. If it wasn't made into a crime sex workers would be more willing to be tested, could more easily be educated and the rate of disease would actualy drop.
Also, sex workers do perform a social function. There are many people out there who enjoy their company as they are unable to be in a stable and loving relationship. Why should they be denied the physical release and pleasure? Again, who is it hurting?