Why can't prostitution be a legal economic commodity?

To further answer this question let us spare the moral and think more about economy, freedom, and pragmatism.

Prostitution as many have known is also another kind of job. The purpose is to earn money by giving services to other people, well, you know what kind of services they are.
Many of them exist in our society. Prostitution also pay for taxes and behave like a normal person, they just have a different kind of job so they’re still good citizens and good for economy, especially at recession times.

People need sex so I don’t see it’s wrong if other people find a way supply each other to sustain their life. This is the same like when we’re sick, other people provide medical treatment for us in exchange for money. So we could see that this is just another economic cycle between producer and consumer

If we think about it no matter how much and how long our government try to banish prostitution they will always still exist as long as the desire to have sex is exist in human kind, which is natural for sexual living creatures. Many women and their families in many countries (especially poor countries) could die because of starvation that is rooted from poverty. If their government approve prostitution as a legal job and erase any law about it they could’ve saved many lives instead of focusing on their egos and feel proud of their current achievements and religions.

As long as they are healthy and have a legal proof their job is not very different than a job of a massage therapist. So, aside from moral issue it’s not hard to see why prostitution couldn’t prevail as legal job. Why are our government keep insisting on banishing prostitution while they have approved polygamy/polyandry (since it almost have the same pattern) if their decision based on humanity and morality?
Why would our society seem to support this rule and sustain the perception of bad prostitution? Is it possible that one day prostitution would be legal in your country? What should have happened for that to becomes a reality?