All currency are used in Illegal activities whether it is bitcoin or USD or any other form of money because it is used to buy things so that it used for illegal activities such as gambling, buying drugs and other. As long as it is form of money it can be used into Illegal.
Yeah, every currency is used for illegal activities. The goodness with it is the convenience that each currency provides. On illegal transactions USD is used much and at the early days of cryptocurrencies existence bitcoin was used as a storage token for illegal fund transfer and eventually this got changed when the coins become more potential.