Why do many rationalists like cryptocurrency?

I have noticed that many people in the rationalist community seem to like cryptocurrency. This seems odd to me, considering how many rationalists also care about effective altruism. Cryptocurrency seems unethical to me.

As far as I can see, cryptocurrency has negligible value. It solves virtually no problems that warrant solving and is mostly useful for criminal activity. Cryptocurrency does cost a lot of electricity, though, so it looks like net negative utility to me.

I understand that you can make money off Bitcoin and other major cryptocurrencies, but this seems to me like unethical speculation. It is a “bigger fool” scam—technically not a pyramid scheme but ethically equivalent. You buy a Bitcoin and hope to later sell it at a higher price to a “bigger fool”, who in turn hopes to sell it to a third fool—while creating nothing of value.

I gather that some people think of cryptocurrency as a political project, a kind of money supply that is out of government control. This project seems misguided to me. If cryptocurrency does become a useful tool against government control, then it is guaranteed to be co-opted by oligarchs who will probably be worse than governments because we cannot vote them out.

Am I missing something important here? Those of you who like crypto, could you please explain where you think I am wrong?

Thanks!