They are the biggest banks and multinational corporations on a global scale. Criminal money laundering The banks are involved head over heels in the criminal laundering of ever vaster sums of money, without which the giant drug dealers could not possibly survive. There is a silent, secret but nonetheless deadly partnership between the drug lords and the lords of high finance. They need each other. The drug business could not stand as a big business without this relationship.
Big business is characterized by the chase for lucrative super-profits.
Even if the money could be hoarded, idle funds bear no interest. For every day, every hour, that millions of dollars are stashed away in places other than banks, much interest is lost. Idle funds are a burden, and not only a financial one. They are the target of raids by the government as well as by other elements of the criminal underworld. In the banks, the money is safe and secure.