Bitcoin allows money to be sent anonymously across a peer-to-peer global network, with no intermediaries needed to validate or process transactions. That has made it attractive to those who want to keep their identity secret, including those buying and selling illegal goods and services on the internet.
Behind the development of advanced technology must have an impact or risk in it. Including bitcoin, many people take advantage of the convenience of bitcoin transactions for less positive arenas, but I think everything goes back to the consciousness of each individual.