This is a misnomer and paradoxical; for it to be tradeable there has to be a financial entity willing to back it into normal Currency.
That said, I do agree that it should not be a recommended way to make money.
There are, but the financial entities are early bird speculators, financial investors at larger scale financial entities, but also just within their speculation departments. And people running those schemes, for the talent pool, that gets attracted to it. As well as people wanting to make money in the transaction process (paypal f.e.).
Now thats my storytelling, and part of the question that remains is, "isnt that always the case - when something new is created - to some extent", and when is the jumpoff point, to it becoming more than that. (Speculation.)
And the answer I've made up in my mind is, that - if you want those currencies to be vehicles to attract talent, you need those oscillating price curves - because those people are interested in potential. And if you want for it to become the new digital gold. you cant have those, and the entire thing gets boring AF. And there is no reason to believe that those currencies will be statebacked anytime soon (national banks spin up their own initiatives, or partner with facebook coin in the US (facebook coin isnt 'crypto'). And there is no reason to believe that any of this will produce compound growth.
Also the issues are manyfold. With POW you have transaction speed and energy consumption issues.
With POS you bake in even more pyramid scheme, than with POW (no 'generational' reward for becoming better, just invest large early and stick to it).
For it to become a legal currency in use, you dont need the decentralized part (use central servers - higher transaction speed).
So wtf.
On the 'people want it' side, national entities usually want to see the transaction record (possible if public), but that could as well happen serverside, and therefore be 'more privacy providing' to most users (depends, privacy from whom..). And digital payment solutions can be created without much crypto decentralization at all. (See Jack Ma.)