This largely illegal profession is one of the oldest markets in the world and, despite efforts, will probably exist for as long as humans (and other animals) exist. Still, while prostitution is argued to be the "world's oldest profession", child abuse is just as old and nobody justifies that.
Contrary to the glamor that the media gives to the image of prostitution (such as films like "Pretty Woman"), there is hardly anything at all glamorous about the trade.
Most women who have become prostitutes were raped as children, came from unstable or abusive homes, suffer from addiction, any number of traumas, and often ended up as runaways before entering the sex trade. Low self-esteem is also a major risk factor, whether or not the girls come from poor familes.
Other women have been tricked or outright forced into prostitution; pimps, who can easily be described as men who have no respect for women and care only about their own gain, are the ones who recruit girls as young as twelve to work for them. The pimp usually lures the young, impressionable runaway by acting as a boyfriend or a father-figure to her, offering support to her... and training her like a dog all the while; once she's under his power, she has little chance to escape.
Even those who willingly turn to selling themselves do so out of desperation to survive rather than because they like the work. Mothers (especially poor, unmarried ones) who have fallen on hard times and are desperate to support their children have also ended up in the trade (like Fantine from "Les Miserables").
The idea of the "happy hooker", who likes her work, comes from the fact that the women usually are putting on an act; it helps them to attract buyers if they're smiling and happy instead of crying and upset. Plus, to quote "Moulin Rouge", they're "paid to make men believe what they want to believe".
Prostitutes range from the high-end call girls and courtesans in the legal brothels with rich clients to the homeless, drug-addicted streetwalkers who prowl the streets and the truck stops at night, shivering in their skimpy clothes, hoping that they will survive the night. The women are often looked on with disdain, disrespected, harassed and attacked, and treated as if they weren't even human. By and large, most prostitutes do not want to be prostitutes.
The pimps and human trafficking rings have full power over the women; the pimps usually take all of the money that the women earn (beating the tar out of them if they make less than the pimps demanded or simply from the littlest act of defiance), force addiction onto them to keep them dependant on the pimps, and generally degrade and demean the women without compassion or concern for their well-being.
The risk and spread of STDs among streetwalkers is almost a nuisance compared to the dangers of the streets.
As criminals themselves, protitutes (especially streetwalkers) are less likely to be looked after by the police than the law-abiding; if she is harassed, attacked, raped, or threatened in any way, the woman in question usually cannot go to the police for help or she'll be arrested; if her pimp is arrested instead and she testifies against him, her life and the life of her family could be at risk.
The women must be on the defense all the time against their abusive pimps, corrupt cops, and the clients who use them; a major cause of death for prostitutes is murder. The woman will climb into the cars of clients (known as Johns) as disceetly as possible to avoid trouble from the police and go with these strangers to secluded places where they won't be interrupted, making her easy prey for serial killers. The disappearance of a prostitute may go unnoticed for weeks before anyone says anything.
Jack the Ripper, the Green River Killer, and Arthur Shawcross were just a few serial killers who targeted prostitutes.
How, pray tell, is it "hard out here for a pimp"? For a man who disrespects and actively exploits and destroys women?
Interstingly, in Sweden, it is legal for the women to sell themselves but it is illegal to buy from them; the punishment goes to those who deserve it: the pimps, traffickers, and Johns. The women themselves have legal protection, rehabilitation, and escape routes.
At the end of the day, prostitutes are human; they were human long before they were used and disrespected and will still be human.