For the most part, I only use my credit card these days. However, having worked in a bank, I saw many situations where people needed to carry around large amounts of cash. Knowing how the government tracks cash is important for people that do large transactions with cash.
If you have ever heard about people making millions (or losing millions) of dollars on currency speculation, you are not alone. I have read stories about being making and breaking the bank by investing in Euros, Pounds, Yen, Shekels, Yuan, Baht, Pesos, and a slew of other currencies. From the grand entrance of the Euro to the Asian Currency Crisis in the 1990s, the Foreign Exchange, or FOREX, markets are an important investment opportunity.
I am nearing a vacation that is going to take me to cities with two foreign currencies. While my international travels to the Caribbean and Latin America allowed me to use my US dollars, I am not planning on the same luxury in England and the Eurozone.