Banks are regulated and want a proof of the origin of the money. In Europe even car dealers or jewellery shop want it. Because otherwise it would be money laundering. Of course it is hard to provide a proof if you have the money in your pocket.
So, say you have $10 million after laundering it through a business, and that's used to invest in housing, and that doubles, and later the government identifies all of that original $10 million as illicit because they've identified your laundering method. They are going to attempt to take everything gained, the whole $20 million, under the theory that it was all proceeds of your illicit behavior.
The problem is, what if you already had $1 million dollars free and clear from a settlement or something, and you used that as well, so $11 million was invested and $22 million resulted? Is the government going to take $20 million and leave you $2 million? Doubtful. Should they? That's an interesting question, and depending on how people view the laws involved, 4th amendment rights, and the purpose of the seizing of money, they might come down on different sides of that question.
They were basically offering money laundering as a service as recently as ten years ago. And given how long those court arguments likely take that's recent enough.
https://www.investopedia.com/stock-analysis/2013/investing-n...