I would think this is a rather fringe use-case, depending on what things you define as criminal. I mean, in the original technolibertarian/cryptoanarchist formulation, cryptocoin was meant to free folks from being persecuted for such "non-crimes" as tax evasion, securities fraud, prostitution, narcotics trafficking, arms trafficking, etc. If you include this stuff, I think it's a sizable fraction, but still not generating as much demand as the speculators are.

If you really just mean "remittance payments to OFAC-listed countries", then I can't imagine that's a big use case at all, especially since the first world, the source of most of these remittances, has made it pretty difficult to turn cash or legally-earned in-my-bank-because-i-cashed-my-paycheck money into crypto without a paper trail.

Also, the OFAC countries are just not the most popular places to send remittances from the west, the reason being that its just really hard to do so. This in turn reduces incentive for otherwise remittance-sending immigrants from those countries to go to the West, which in turn lowers demand for the service. If the US were to suddenly put Mexico on the OFAC list (not unthinkable given the current administration), there would be riots in the streets in both countries, because the scale of these payments mean that large fractions of both economies are built on the flow of this money (in Mexico), and the labor it motivates (in the US).

>>cryptocoin was meant to free folks from being persecuted for such "non-crimes" as tax evasion, securities fraud, prostitution, narcotics trafficking, arms trafficking, etc.

It's important to clarify that "securities fraud" here refers to what statutes refer to as securities fraud, and not any actual fraud involving securities.

Any sale of a non-registered security is termed "securities fraud" by the Securities Act, even if the sale involves zero fraud. The term, as used in the statutory context, is a misnomer, and an Orwellian attempt at misleading the public into believing there was a victim in the transaction.

Generally libertarians like the cypherpunks do not object to laws against real fraud. It's the victimless crimes like prostitution, trade in unregistered securities, drugs, etc that they believe should be free of prohibition.

Anyway, to your point, there are legal industries where traditional financial players cannot operate, like the legal cannabis industry, due to everything from corporate policies being slow to react to the change in laws, to reputational risk, to non-binding but still influential guidances and warnings from regulatory agencies (e.g. Operation Chokepoint). These also might be/become natural sources of demand for cryptocurrency.