Unpaid internships are legal so long as the business receives no value from the intern, and the courts would uphold that, if ever a case came before them about it.

In practice, the only people who have the option of taking an unpaid internship - where they have to spend many hours a week in a workplace that doesn't pay them, to the exclusion of spending those hours in a workplace that does pay them - are already finanically stable enough to do so, probably because of generational wealth. AOL and UO were exceptions, probably because people wanted to participate in those communities in their spare time, as a kind of hobby.

Those people are being inducted into the system that propagates that generational wealth. It's not in their best interest to protest not being paid when they should be, because the repercussions of doing so would be being excluded from that system. So it's highly unlikely that any real "this should be a paid internship" case would ever be filed. The amount of hours which would be ordered to be compensated, even if it was treble damages, wouldn't be worth the cost of going to court, let alone being excluded from whatever industry.