Can you kill someone with a car, knife or brick?.. and we still use them to drive, cook and build ;) And if you want to go deeper on this subject there are few investigations being made on that subject and it has been proven that just a small fraction of cryptocurrencies is being used for that kind of activities... I will tell you one more interesting thing that not many ppl are talking about. Crypto is not so great in hiding your transactions, payments, and activities because when your identity is reached through the banks payment or some other way all your transfer history with all buy and sell transactions is available on the blockchain.