Hiding money from the government is still hiding money from the government and digital forensics just make it easier to get caught. It’s not impossible to trace a coin join. If you are a criminal cash for gold would be a much more private way to hide but I’m personally not willing to risk money I want for old age or to leave someone else when I die to an illegal process just to dodge taxes. I pay more for income tax than I do for capital gains. If you need crime you are desperate.