Anyone who says Bitcoin is used for illegal purposes should be ignored. They obviously are newbies learning about Bitcoin for the first time.
Bitcoin is being used for illegal purposes. Ramen is used for illegal purposes.
Ban ramen, Bitcoin, prison yogurt, barter, USD.
Bitcoin is significantly easier to track than cash or Ramen. If you want to get rid of illegal Bitcoin transactions you simply need the government to care. But the real risk is the ramen/USD trade, that can't be tracked. Ban Ramen?
Right...
Financial crime is not the only possible use of cryptocurrencies, but it is the only use case where it is potentially better than dollars.