And a car sharing scheme would need physical cars, making it pretty easy to take down the system or haul the car owners to court if the service is breaking laws.
Stopping crypto-mixing is much easier then stopping money laundering.
At some point, your internet crime ring will have to procure goods from the rest of the world. If the government wanted to crack down on it, they very easily could.
The underground drug markets only work because illegal drugs enjoy enormous profit margins (And because they are incredibly easy to conceal), due to lack of legal competition... And because, unlike crypto-currencies, cash transactions are common and untraceable (Which makes money laundering possible.) How is your illegal self-driving car company going to make those margins? How are they going to be able to afford to pay off all their suppliers (Who will charge a premium due to the legal risk), to keep your operations under wraps? How are you going to get customer to pay you, when it's illegal to drive your cars round town?
During prohibition, Al Capone was running moonshine, not beer. There weren't enough margins in beer, to risk federal prison. There aren't enough margins in <Whatever illegal bitcoin business you want to run, that doesn't involve a meth lab, or burning people alive in oil drums>, either.
