That doesn't stop cryptocoins from being the currency of choice for criminals that need completely anonymous digital transactions, which is why they are the standard for the online black market and for ransomware. It's hard to argue of the advantages of cryptocoins while in the same breathe arguing that cash is better for crime.

The bigger issue is that very few people want to hold onto cryptocoins if their goal is to spend the money. You can't really buy much directly with cryptocoins in comparison to cash which is universal. I can't use it at Walmart, I can't use it at McDonalds, I can't use it to buy a house, I can't use it damn near anywhere. The only way I can use it is through a scheme that converts it to cash first. No criminal wants to add that papertrail step to their operations.