1. Chinese people using Bitcoin to move money outside of China, thereby bypassing government regulations.
2. People building private marketplaces (even if it isn't drugs), thereby avoiding paying taxes.
3. People doing blackmail and extortion directly and using crypto to try to avoid having the money tracked back to them.
4. People stealing electricity and then laundering that stolen energy by converting it into crypto which is then sold for money.
Really, name me any big crypto-based operation that actually pays sales taxes in all regions in which they operate.