Why do the government or even exchanges take actions on the mixer coins, because the are involved in a large volume, this alone is one of the reasons why they take closer attention on the coin and try to make a trace to see where its coming from, mixers don't make a trace on whatever amount of coin sent for them to mix, while exchanges can do that when there is a suspicious alert in which caught the attention of their AML policy, most people that mixed coins don't even directly send them to exchanges, they would have prefer the use of a non custodial wallet in case the amount involved is much.
I do not think that they take action on all coins that passes through a mixer. Do they?
While some people may use Mixers to cover up their illegal activities, I like to think that there are others who use mixers more because want to the anonymity in every sense of the word and not because they are doing something shady. Secondly, I do not support tainted coins passing through mixers but then isn't it dumb that after using the mixers they go ahead to send it to an exchange? Why not send it to a decentralized exchange. Or will the government be able to trace it and flag it and then they lose their coins if they do?