It applies to 99% of professions, most of the time, at least partly.

Why should an illegal immigrant stay with someone else's children for less than the legal minimal wage?.. Why should a street leaf blower kill his hearing forever? Do you think that having sex, even when you are not interested in it, is worse than leaf blowing?? I do not think so - at least you are mostly horizontal, so there is some kind of rest for you, and you are not subjected to harmful noise pollution.

Etc. etc.

In other words, the question should not be phrased "Why is prostitution illegal?" but "what is the reason that market economy applies to most things but sex is somehow exempt?". What is it about sex that makes it so damn special that we disallow the market economy with respect to sex??? No rhyme or reason.

- because the body is sacred? Well, it is great, so people who think that the body is a temple should treat their bodies and the bodies of their friends, lovers, etc. as sacred. People who do not like the idea of prostitution should neither become prostitutes nor patronize prostitutes - that is it, easy.

I very much welcome the idea of prostitution, because affordable, relatively safe, legal prostitution would prune the ranks of men who are in the dating world. The way it is, after those two encounters, one with a p-doc in SF and the other with this lawyer in SF, I am no longer sure what is going on. I do not know anymore when I am contacted by someone on a dating site (I haven't been on OkCupid since Dec, but I plan to check the inbox), whether the person is desperate for sex or has a genuine interest in me. Not that legal prostitution would fully solve this problem, but it would contribute to removing people who are desperate for sex away from the pool of people who find me special in some way and want my company.

As for married men... I think, the way it was explained to me, that people want to be preferred. I fully understand that. That is the only part of monogamy that I understand. Yes, people want to feel special, unique, chosen, and preferred. There is some limit to how much they want to My late grandmother told me a story about one of Hemingway's four wives; the wive invited her girlfriend to live in their house and eventually Hemingway started an affair with the wife's girlfriend and left the wife and married the wife's girlfriend. I am looking at Wikipedia and it appears that this was about his first and second wives:

Elizabeth Hadley Richardson
(1921–1927)
Pauline Pfeiffer
(1927–1940)

OK, so, per my grandmother, Hemingway said that women should not invite their girlfriends to stay in the same house with their husbands because the created temptation might just be irresistible...

So between the two extremes - the world where sex outside of marriage is punishable by corporate punishment and the world of Hemingway and his first and to-be-second wife, people want to stay somewhere in the middle, for the most part, as far as I can understand.

Why? Because of what is fun.

Is it fun to have sex with your husband knowing that the only reason he is having sex with you is because he does not have other options for he would be shot to death if he has sex outside of marriage?

No, there is no fun in that.

The fun part is to feel special, chosen, preferred, and unique. The best. For that, the other party should be doing what he is doing out of his free will, and not because of vows, a court order, fear of capital punishment, fear of God, sense of obligation/duty, fear of societal disapproval, or anything of that kind.

So to the extent that prostitution will make sex outside of marriage more easily available (I doubt there would be that much of a difference, though, these days), the wives whose husbands do have conjugal sex with them would rest assured knowing that the husbands have sex with the wives because they choose to do so and not because they have no other options.

In general, though, prostitution throughout history supported and bolstered lifetime monogamy (meaning, marriage that lasts until death and not actual sexual monogamy) because of compartmentalization. Now people marry, then meet somebody else, remarry, etc. Well, like Hemingway with his four wives, Picasso with only two wives but many mistresses, etc. This is all fairly modern - in the past, it was different - the men of nobility would have one lifetime marriage to an equal (equal based on class) with various sex partners from among the lower class women and prostitutes.

I do not think that in reality legalized prostitution would have any effect on marriage statistics these days, but it least it would serve to pre-screen men on the dating sites, and that would be such a big help!