1) Why is it illegal ? ( with out to much complexity)

I think this answer can be found only in legal theory.  Laws have two distinct purposes to follow the social norm and to alter social norms.  Obviously, prostitution is the social norm and the law was designed to alter it.  There are many theories why it is illegal.  The most obvious one is religious.  The US is very Christain despite the alleged separation of chruch and state.  


Karl Marx believed that back in the cave man days women had sex with many men and bore children from those various relationships.  The men rewarded the women with food to care for the children and themselves, it was like prostitution.  But the men did not like not knowing who their children were,  so they developed marriage as a way to ensure that the children they cared for belonged to them.  Then they wrote property rights controlled by law to deprive women of property. If you recall not too long ago women were not allowed to own property.  Remaining prostitutes were seen as women rebelling against the system and laws were needed to stop it,  so it was made illegal. Anyway,  I prefer Marx'es theory that prostitution was made illegal to perpetuate the marriage system and to deprive women of the right to own property.  In order for the system to work they had to make it illegal.  Of course Marx's theory has as much validity as anything anyone makes up, but it sure sounds good to me.  



2) Did the law/s change at some point? circa:

I don't know.  They vary in wording but the mostly the laws in all states on this issue are the same.  I doubt they have changed much.

3) Wasn't Mary Magdeline a prostitute?

Yes, but many of the bible stories have never been proven.  Some people don't even believe in Jesus.  (oh the shock and horror!)

4) Isn't it a "Freedom of Choice" issue which should govern the legal aspects of this?

There are lots of things that are illegal that can be argued should be a freedom of choice.  Recall alcohol in the early 1900's,  drunk driving used to be okay,  beating children used to be acceptable,  of course wife beating used to be ok,  and some drugs were okay back long ago.  Freedom of choice is never enough to make something legal.  Choosing to kill someone does not make it ok.

4a) Constitutional/Bill of Rights issues?

Some people like to think that the right to privacy should protect people from laws against prostitution.  Many people think the government should stay out of the bedroom.  Yet historically the government has always been in our bedrooms.  Recall that sodomy used to be illegal regardless of gender,  even though it is aimed at homosexual men.  Abortion used to be illegal and many people today think it should be a constitutional right, but it is not.

I don't know exactly why it is illegal, but it is and you can get busted because it is.   I think that is the key.  Just know it is illegal and it will continue to be ilegal probably for the duration of our lives.