Intoxication with crypto makes people too blind to see the simple things in simple ways. They go hyper-technical and philosophical and forget the fact that crypto encourages and forms the basis for payments in ALL ransomware attacks in recent times. How hard is it to see that banning crypto would help reduce the crime?
How do you "ban" crypto? Even if you think it's evil and doesn't have any useful applications that "pandora's box" has been opened and can't be closed anymore.
What would you rob from someone on the street, who isn't carrying any expensive item, especially no fungible ones?
In the past, there were often abductions for ransom. This has mostly stopped, as the police always got the abductors when they tried to collect the money.
In my country there are still ransom abductions and all paid in FIAT, one way or another criminals are going to still do ransom attacks without fungible cryptocurrencies.