An intermediary currency only has use as such when its value is stable.

And it only has use as a store of value when it is stable.

And it only has stability when it has intrinsic value, or is backstopped by a trustworthy revenue stream. (And is not debased by massive expansion if the supply.)

And if not useful as an intermediary currency or a long-term store of value, a currency has no legitimate usefulness at all.