Unless you only take payment in trade, you deal almost exclusively with imaginary currencies. All currency is fiction to streamline an economy so we don't have to expend an inordinate amount of time and effort in a barter system. Most currency isn't even printed, just numbers in computer systems, sometimes with a dead tree paper trail.
Sure, but there is a real system in place that specifies that I am able to get milk per litre for 2 EUR, and purchase a coffee at the local coffee place for 3 EUR, not only that during that entire time I am able to have paper in my hands which has "value" because EVERYONE considers it to be valuable.
I can't do the same with Bitcoin, I can't have paper in my wallet, I can't go trade it for real goods right now. There is a lot of fluctuations in the price of Bitcoin, since it is entirely virtual it can easily be attacked and there are no systems in place for me to get my Bitcoin back if there is a fraudulent transaction.
