General Discussion

That's always been skirted around.
A wealthy man or organization will coax, bully or threaten as needed.
Through the US worship of celebrity and acquiring money while not going to jail, the wealthy man or organization is also being portrayed as a socially beneficial force; not an obvious mobster or organized crime.

At best, a struggling family that is just glad to not have to financially worry about at least one of their children that can land a job that might get them into the rarified sphere of the rich. And that family won't have access to legal protections to prosecute should their child be abused and hurt.

Other children came from broken homes or were looking for emancipation from the chaos of their lives and basically "ran away" for a better life in their view.
Their parents ether weren't there, didn't care, or had been overwhelmed and gave up, letting the child go free so long as they could check in.
Any parents, parent, or guardian that may have been available as a caregiver also most likely did not have access to legal protections for that child.

Other children may have eagerly been sold by parents or guardians for money.

But no matter "where the parents were", this is still a situation where wealthy men or organizations used their power to coerce or procure vulnerable children into the horrific situation where they were turned into non-human disposable play toys for the amusement of idle, bored rich sociopaths.