It may not be the absolute most useless, but it's awfully niche. You can use it to transfer money if you live somewhere with a crap banking system. And it's very useful for certain kinds of crime. And that's about it, after almost two decades. Plenty of other possibilities have been proposed and attempted, but nothing has actually stuck. (Remember NFTs? That was an amusing few weeks.) The technology is interesting and cool, but that's different from being useful. LLM chatbots are already way more generally useful than that and they're only three years old.