All currencies around the world are being used as a currency and as a way to speculate with them, when those currencies were backed by gold there was no point in speculate with them because all the currencies were backed by a certain amount of gold, but now that no longer is the case and every single currency fluctuates depending on other currencies then you can speculate with them and that's how the forex market was born, so what you're saying doesn't make a lot of sense we know the dollar is just a currency and it is used as a way to speculate with other currencies and yet is used all over the world, if bitcoin is widely adopted its volatility will go down and so we will be able to use it as both.