CipherTrace just published their Q2 Cryptocurrency AML Report and found it interesting that Bitcoin still reigns king in dark markets and cybercrime. Most people associate privacy coins even just 4% involve Monero.
Even in the case of malware and ransomware, ETH used in only 1% of instances and BTC used in 98% of cases.
https://ciphertrace.com/q2-2019-cryptocurrency-anti-money-laundering-report/I'm not surprised that crypto has been used in dark market but to use Bitcoin instead of some privacy coins like Monero, maybe most of them only knows Bitcoin and not those privacy coins that is why they are only using Bitcoin.
Not surprising because anything that has value can be use in good or bad things. This will increase in the next years for sure.