The problem with "We'll make our own payment processor for blackjack and hookers" is that banking and payment processing is highly regulated so there's a huge barrier to entry, plus most people don't want to have to create multiple accounts to buy things online.
I'm not a crypto guy or anything but this might be the only use case I can see for it since it's still unregulated and decentralized enough that campaigns like this wouldn't cripple entire industries.