I wouldn't have said it in such an exteme, but it is true that prostitution flourishes and is more popular in places where promiscuity is forbidden or looked down upon. The more sexuality and sexual activity is open amongst people the less need there is for people to purchase sexual gratification.

Which is why prostitution no longer exists in Europe, right? In fact, it is actually legal in some of the most liberal countries there. Those countries are hardly sexually restrictive, and yet prostitutes make money there. But how can this be? Oh wait, I know: it's because that theory is bullshit. Just because you can have sex doesn't mean other people want to have sex with you (for nothing), let alone right when you happen to be feeling randy. Or maybe you're just butt ugly or a total creeper and can't get the girls you find attractive without paying for sex outright.

That's why prostitution exists. Not because the government restricts your sexual opportunities (except maybe in the most restrictive cultures on the planet) but because life restricts your sexual opportunities.