For example, creative jobs in NYC. There's tons of illegal, unpaid internships and tons of companies who don't want to pay. I know several animators working in the industry there and often it takes them 6 months after a project to get paid and frequently studios try not to pay. I know a couple of people who have worked in the industry for 6 or more years and never been able to get a paying job.
Imagine working in an industry pulling 60+ hour weeks for 6 years and never getting paid for your work...and that's after being saddled with 200k in loan debt from an art school. There are so many people in that area willing to work for free and are used to it that it's difficult to find long-term paying work.
There's a vast chasm of difference between "right to work" and "right to be paid for your work".
Just because it's "artsy" doesn't make it more okay.
Because after all, open source gives us software for "free". Much of this software would otherwise have to be written commercially, so one can make the case that people who write software for a living deserve to be protected from this open source nonsense.
It's highly probable that for-profit bootcamps using volunteers would be in violation of the long-existing law.