Having known people who were caught up in the cycle of addiction, I have witnessed first hand the worst of this business. There are what I call "extended pimps". Even though these girls may have told you they weren't forced to work, c'mon - their money was still ending up in the hands of their dealer to feed their addiction. If they owe for fronts or need a phone card and they're broke, sometimes the dealers (or others) will do them favours - so they have to do what they do to avoid being beat up or worse, so they're still caught up in the cycle of having to work.
If you're a prostitute and owe a dealer money and can't pay him, see how fast you'll be under his/her thumb.
And this can happen to anyone at any age, not just young people.
And the person does not have to a drug user themselves. I have known of girls supporting their spouses' drug or gambling addiction by working so they could try and keep a roof over their heads.
I know a woman who is in her fifties who advertises on CL (as much younger) and does not have a computer. Up until recently she depended on her dealer to post her ads. If there was a day he didn't have product, he wouldn't put her ad up because he didn't want her making money and buying from someone else. Her whole reason for working is to pay for her addiction but she will tell you that no one makes her do anything. It it not the lifestyle I could stomach.
Another example is hanger-ons, so-called friends and boyfriends who encourage the girl to work so they can "party". They don't pimp her per se, but because maybe someone is providing a place to crash or do business, their motive is "encourage" the girl as much as possible to work.
And has been said before here, even if someone is being co-erced to work, often they will not want to go against their perpetrator, so it is very hard for the police to make charges stick some times.
Being under-age is a little easier for the cops to make a procuring charge stick, but the people orchestrating these things are like cockroaches. The moment you turn on the light, they scatter. And even if you do catch some of them, there are hundreds waiting in the wings.
It's so sad, and no matter how the laws are changed, I believe we will always have this element of society attached to business because they view it as quick and easy money to get what they want.
It's nice to think we are all independent in that we work when we want, how we want with no one telling us what to do, but some have chosen a lifestyle that although it may start out like that can get very ugly as lines are crossed.