They do. There are services (which require quite a lot of trust) who propose you to take a bitcoin payement, and will give you back this amount at a later time (a few days) on the address you desire or splitted in several addresses
If done correctly, this can effectively "launder" bitcoins. However, the likelihood of some of these services being traps is quite hard.
I think that people who believe that bitcoin is great for tax evasion of criminal transactions are there for a surprise. It is but one brick in the platonic society of ideas that idealistic cryptoanarchists try to build. First, there were cryptotools, and identities and pseudo identities could be verified, communication could be kept private. Then there were darknets, and ideas could be exchanged anonymously. Now with bitcoins, money can be exchanged. So right now, what you can do totally anonymously is buying dematerialized service or data. It is not a good tool for buying a yacht without the IRS knowing it, and it is not about that.
More bricks will come: people are currently making schemes to create pseudonymous companies, to make some kind of contracts enforceable, to manage trust between entities with no history, etc... It is an interesting subject to follow.