Let's see pussycat do you have the balls to reply in less than 4 lines?
A mangy dog always returns to its vomit
Let me ask another question.
What makes a currency useful?
Basically, currency allows you to separate in time two otherwise inseparable events (read one event), namely, an exchange of goods. What would be a one event in a barter deal turns out to be two essentially independent events in the exchange of goods mediated by a currency. This offers you a possibility to exchange virtually anything for anything else (which is not the case with barter), that's why currency is useful
Just in case, Bitcoin is not a currency, for the most part, as of yet and so far