Read the quotes from the union rep in that article. You tell me.

Priority one will be keeping it legal. Any bad press is aid to folks like me. There won't be any bad press, because there are no sex slaves in our industry, just like there are no incompetent teachers at public schools.

Casinos are billion+ dollar investments where regulation helps the client and being able to legitimately raise huge sums of capital lets you crush the mob. After decriminalization you can play in a seedy backroom with an unknown rake or you can have a business conference on the corporate nickle in a five star hotel where the rake is established as a matter of law. Customer preference wins.

Regulation in prostitution tells client that they can't do what they are willing to pay to do, and it is not capitally intensive and does not reward megascale. After decriminalization you can have the sex that they allow you to have or the sex that you want to have. Customer preference wins.

I read the article but didn't find compelling arguments to say that better oversight and regulation wouldn't reduce criminality. The question of whether widespread legal prostitution is good for a society is different to the matter of making it crime and exploitation-free. I don't have an answer to that ethical question so I wouldn't want to end up arguing that particular angle with you. It's just that the claim that it is inherently impossible to regulate effectively is quite a major one and perhaps people haven't tried hard enough, perhaps as a result of prejudices many of us share.