It's very simple really. Please point out where on the below list of Top 20 contributors to a randomly selected US politician [10], in this case New York's Chuck Schumer, can one find Standard Chartered, Barclays, or HSBC?
And there's your answer, which should also explain why banks such as Goldman Sachs, Citigroup, Morgan Stanley, JPMorgan, etc, will never be subject to the same kangaroo court in which suddenly everyone is shocked, shocked, that banks were manipulating Libor and laundering money or doing any other thing which bankers do day after day, every day.
Oh yes, there is an election coming up too...