"Napoleon was clear about why he set up the Bank of France in 1800: He wanted a bank to lend his government money when he needed it. As monetary economist George Selgin wrote, “The idea of credit which existed in the mind of General Bonaparte boiled down to this: that he might have all the credit he wanted, if only he could establish a bank he could control, and award it a monopoly of currency.” This nicely sums up one essential function of central banks: financing the government of which they are a part. If you want your government debt to be thought of as nearly risk-free, the central bank has to be willing to buy it at all times.
Somehow, the central banks don’t discuss this service of theirs in their brochures or their public statements. Nonetheless, it is a critical element of whether central banks are, or ought to be, “independent” as they wield their great financial and economic power. If independent, how they are to be accountable, and to whom? Upon the answers to these questions depends the legitimacy (or lack thereof) of these unelected wielders of power in a democracy."