It's hardly a legal problem, there are plenty of countries and US states where many kinds of sex work are perfectly legal, and having your life ruled by credit agencies is far from universal.

I understand that with decent regulation illegal goods can't just fly under the radar anymore, I'm just saying that in the current ecosystem there is a use case for this fake money where real money simply cannot be exchanged reliably. In an ideal world we wouldn't need fake underground value transfers but the world is far from ideal.