The theory and reality don’t match.
Drugs are likely the number one things bought using crypto as currency.
Firearms and pornography can be bought with dollars if you’re using crypto to buy them or other unpopular goods or services, you are veering dangerously close to black markets, which invite regulation.
Neither pornography, nor legal funds for unpopular cause (think WikiLeaks), or dissident creators are criminal. At least not in the US or Europe. But they are still blocked by the main payment processing companies.