For all it's outdatedness, Bitcoin is actually used as a currency, but typically for high value items such as real estate or private jets, as the fiat mechanisms to transfer large amounts of money, especially across borders can be terribly unreliable and costly. Bitcoin, even used in its largely original form, can be (and is) used to transfer arbitrarily large amounts of money anywhere in the world, conclusively and trustlessly, without intermediaries, within an hour, or more typically ten minutes.

There has never existed a currency that has had such properties previously.