> An adult entering into a voluntary contract is profoundly different than a child being forced into work, in fact it's the main thing that it means to be an adult
Ah, okay, let's deal with adults: can you volunterilly sell your organs, sell yourself into indentured servitude, or into prostitution? Can you buy heroin or uranium? Can you at least open a coalmine without health and safety and let other people agree to work in it when they know they will get blacklung? No, you can't even buy some financial products without proving you are a sophisticated investor.
You are not allowed to do shit like that because when we allow business to profit out of misery and misfortune of others, business will purposefully trap unfortunate and vulnerable. It isn't an adult vs another adult -> it's one man vs multi billion dollars of lobbying, marketing and legal department.