The ONLY reason?
Banks are in business to make a profit.
The means by which banks can make that profit are determined by laws, regulations and market conditions.
IF banks committed fraud by misrepresenting sales packages of loan portfolio's, then those responsible should be prosecuted to the fullest extent of the law.
IF Federal guarantees or requirements induced the banks to qualify certain lenders, then those responsible should also face the consequences of their actions.
This is QUITE honest.
Banks and politicians are in business to make a profit.
They’ll tweak laws and regulations to increase those profits while transferring risk.
That is NOT honest or moral.