“Dirty” money is such an expansive term that encapsulates huge sums and many distinctly different schemes. The Guardian actually stated that the influx of cash from crime syndicates propped up the banks and significantly contributed to some banks financial health—- thus helping during the economic crisis. This money is part of the economy and it is hard to entirely crack doen on it less risking unforeseen issues.

https://www.theguardian.com/global/2009/dec/13/drug-money-ba...