The purpose of mixer was not for money laundering and it to provide people the privacy they need which is the reason why they are legal not because hackers seized the opportunity of using it.
And what if it was used for laundering. It's not the fault of the mixer that someone uses it to commit a crime.
It's also not the fault of a knifemaker that his product can be used to kill
They are literally useless if you don't have anything to hide.
And what if I simply earn coins every month and want to hide from people who know my address like my employer what and where I'm buying?
Most people have something to hide. If you keep exposing your privacy to the world sooner or later you'll regret it.