Why would they touch them? It's an easy income source for the government, and one that's recurring as well because you know that the profits made by banks are far higher than whatever they end up paying in fines. Governments happy because they receive hundreds of millions in fines, and the banks happy because their profits are largely still there.

If governments were genuine, they would increase their fines to such degree that the profits made by banks would not only be nullified, but the bank actually loses hundreds of millions. The current system is set up strictly to enrich the government and allow high level money laundering to take place because they get a slice of the pie.