You've got an entire darknet, you've got 80% of the world's population living in areas where censorship resistance is valuable. Chinese wanting capital flight, inflation infested countries looking for an alternative, areas of high political risk and instability.
To say its not really useful for anything is just facetious. Bubble sure, tech isn't there yet sure, no future use cases, now that's definitely not true. Will the use cases be worth 400 billion, that's a better question.