Isn't evading pesky legal restrictions pretty much the entire point of cryptocoins? Sanctions, capital controls, banned substances, ransoms ...

Yes? Isn't it the purpose of crypto to avoid centralized restrictions? The person can still pay taxes by declaring it. Either way, when he turns crypto into fiat, he will have to explain its origin to his government and eventually pay taxes.

dont ask dont tell

a major crypto usecase is terrorist financing/sanctions avoidance