To be a currency, you need inflation. Otherwise you have an asset. We can see this from European history: before 1492 it was common to hoard gold as if it was gems, rubies, sapphires. It had limited use as a currency, and only at the highest levels of the economy, never at local levels -- it was traded among the very wealthy, the same as assets might be traded among the very wealthy. Only after 1492, when gold and silver started to pour in from the New World, did gold and silver become useful as everyday currencies. The French historian, Fernand Braudel, spoke of the "the price revolution of the 1500s" because inflation managed to average 1% a year for the whole century, which was likely the longest and largest sustained inflation in history up till that time. It was that inflation that gave birth to the modern world, and gave us a world of currencies and wage-work. Because crypto lacks inflation, it cannot be used as a currency. It will remain an asset.