At first it was just a taste.
It was hard times, and Wall Street banks just needed a little something to get by.

Antonio Maria Costa, head of the UN Office on Drugs and Crime, said he has seen evidence that the proceeds of organised crime were "the only liquid investment capital" available to some banks on the brink of collapse last year. He said that a majority of the $352bn (£216bn) of drugs profits was absorbed into the economic system as a result.
..."Inter-bank loans were funded by money that originated from the drugs trade and other illegal activities... There were signs that some banks were rescued that way."

But the rush came too easy, and while people looked the other way, Wall Street banksters quickly lost self-control.

The authorities uncovered billions of dollars in wire transfers, traveller's cheques and cash shipments through Mexican exchanges into Wachovia accounts....
It paid federal authorities $110m in forfeiture, for allowing transactions later proved to be connected to drug smuggling, and incurred a $50m fine for failing to monitor cash used to ship 22 tons of cocaine.
More shocking, and more important, the bank was sanctioned for failing to apply the proper anti-laundering strictures to the transfer of $378.4bn – a sum equivalent to one-third of Mexico's gross national product – into dollar accounts from so-called casas de cambio (CDCs) in Mexico, currency exchange houses with which the bank did business.

When you get this strung out on hard-core money laundering you will make a spectacle of yourself. Drug cartel money is no longer strong enough.
You require a bigger fix.
One morning you wake up in a sleazy hotel bed with terrorists. Lots of terrorists.

More than 200 people, primarily American service members or family members of soldiers killed in Iraq, filed the lawsuit on Monday in federal court in Brooklyn. Citing more than 50 attacks on American citizens stationed or working in Iraq during the war, the lawsuit accuses the banks of helping to finance the violent activities through their ties to Iran.

Eventually people will notice.

A Senate report released ahead of the embargo time revealed that HSBC’s lax anti-money laundering policies allowed Mexican drug money, Iranian terrorist money, and even suspicious Russian money to enter the U.S. and gain access to U.S. dollar liquidity over the last couple of years.

Your public shaming also brings attention to all your low-life junkie friends too.

Regulators, led by the Office of the Comptroller of the Currency, are close to taking action against JPMorgan Chase for insufficient safeguards, the officials said. The agency is also scrutinizing several other Wall Street giants, including Bank of America.

Normally at this point of public shaming there are tears, apologies, forgiveness, and promises to kick the habit with 12 steps.

But that didn't happen this time. Wall Street decided to go the other way.

The US’s biggest banks are wasting billions of dollars each year trying to track criminal activity, according to a powerful lobby group which is arguing for a radical overhaul of the way the US keeps tabs on terrorists, money launderers and tax dodgers.

You see, the problem isn't all that sweet, sweet drug money.
The problem is that there isn't enough off that sweet, sweet drug money.

Complying with anti-money laundering rules, including the manpower needed to file suspicious activity reports, costs U.S. companies as much as $8 billion a year, the Heritage Foundation estimated in a report last year.
The Clearing House will propose a new system under which banks do not investigate and report every transaction that could possibly raise a red flag, according to people involved in the effort.

That makes perfect sense to me.
Cut me another fat line.
What could possibly go wrong?