It is a boring application of existing hash functions to create a really inefficient data structure. It is impractical for just about a everything including currency, and if crypto took off the hard limits on transactions (iirc) would make its use quite difficult.

Bitcoin is the first currency

I live in an objective universe that I have relatively little control over. My employer won't pay me in it, and I can't go down to the supermarket and buy a loaf of bread with it to feed my family. No one can compel you to use any particular words, but there really isn't a basis for me to think of it as an actual currency beyond being a novelty.

The spices in my cabinet would have functioned as more of a currency in our shared history than what crypto could ever accomplish, but I don't expect my employer to give me sage, either.