All of these things are money, but only the green stuff is cash. Technolibertarians, who advocate a cashless society through digital cash, think that this is a necessary element on our way to an individualistic utopia. Christian fundamentalists see this very same step, the elimination of cash, as a literal sign of the Apocalypse. Think of why drug dealers don't take credit cards. Cash does not automatically create an audit trail, but credit and debit cards do.
Cash is supposed to be anonymous, untraceable and unforgeable.
You don't have to know anything about someone to buy or sell something with cash. You don't have to know where their money came from, either, but after a cursory inspection you can be reasonably confident that it is genuine. These same properties make cash attractive for black market economies. The United States economy used to be on a gold standard. Money itself is nothing - it is simply the idea of value.