That's why every coins that offers absolute anonymous transaction which attracts central authority to investigate it if they sniff something from it such as monero right now, monero leverages identity-obscuring ring signatures to make it unclear which funds have been sent by whom and to whom.
Some coins like this may interesting for people who want to out of radar, remove any trace of their transaction which refers to black market or illegal activities from FBI point of view, so those coins cannot develop/adopted so far such as bitcoin, it will stuck somewhere and drop back if authority begin to trace or ban it.