Bitcoin was never a currency, most of people use bitcoin as an alternate and anonymous payment method without higher transaction fees while others used bitcoin as an investment.A currency is backed by bank or solid collateral but with bitcoin there is nothing like this.
i don't agree with your definition of currency, a currency is something that can be exchange for goods and it doesn't matter if is backed by your government or not, the point of bitcoin is to have a currency without third party that can be used to purchase anything like dollars or euro