I downvoted you because neither of your links clarified why cryptocurrencies wouldn't satisfy a micropayment niche for 402 negotiation, other than "they're a Ponzi scheme." If you'd discussed Brave BAT, or the latency issues involved with posting a transaction or the dust issues with small payments, it would have been on-topic.

They are specifically NOT a Ponzi scheme, they are a new kind of scam.

And isn't it obvious it can't satisfy a micropayment niche because ... it's a scam? Any moment the value of it can drop to zero, someone might walk away with the contents of your wallet -- and that someone might be your exchange. All of these had examples.

> Any moment the value of it can drop to zero

As opposed to... what?

> someone might walk away with the contents of your wallet

Completely depends on how much you care about securing your wallet. I wouldn't say this is a common occurrence at all.

> and that someone might be your exchange.

An exchange is where you go to trade currencies, why are you keeping your money there? And how is that a problem of the currency?