[hvidgaard]

Problem is that the coins can be traced, so they need to spend them anonymously.

[hackerboos]

Couldn't they tumble the coins and cash out?

[Xdes]

Tumbling simply makes the accounting harder, but not impossible.

[hvidgaard]

Even if they do, the mixing service must be anonymous too. The blockchain provides irrefutable evidence, and you need at least one step to make the coins anonymous.