AML laws exist to protect the excess profits of banksters, by preventing competitive new firms from entering the market.
They are not enforced when huge firms get caught laundering billions for drug cartels. At most the bank pays a small fine, and it is not disclosed publicly.
If *you* do anything with BTC, the AML laws will smack you down.
If banks do something with BTC, they are too big to jail.
money laundering is indeed a scale-driven racket: you must _appear_ to be doing something to prevent it, e.g. hire 100 incompetent people to review flagged accounts who then do nothing, so you can say "look, i'm really trying to stop this!".
the trouble with a mixing service is that, on its face, you're selling the service of outright breaking AML laws as opposed to feigning compliance. that's not to say that the service isn't valuable for BTC holders who have only a couple options: (1) zero privacy where all your tx can be traced to you personally (this is worse than existing banking systems) and (2) mixing your BTC so you have pretty strong privacy (done right, this is substantially better privacy than you can get using most banks).