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I think we can surmise what can be the answer to the OP's question.
What it gives them pressure and putting their ends because if the law enforcement hunting them down.
The sad story is that they are allowing scammer and some illegalities used the services that brought them into trouble. If they not allowing it the same thing that other mixers do, it surely they still exist at this time.
Mixing services keep an individual's privacy as to how it works but somehow gives the opportunity for the scammers to hidden. But that is not the case right now because mixing services don't allow that thing to succeed if they get noticed and having suspicious activity. They don't want to ruin their image and they also don't want to be in question by authorities which makes them still alive.