Currently bitcoin has been widely used for crimes because their crimes are difficult to trace if transactions use bitcoin, I think that mostly it is used by common people like you and me.
sinvce the bitcoin made. only the bitcoin and not none other cryptocurrency . there's a crime activities that the bitcoin involve. if you know the site called deepweb. this site is almost at pure crime activities. illegal firearms ,illegal drugs and other illegal sell in this and you buy it using the bitcoin. also, you will allowed to hire a killer .