One extreme: At some point far in the future, perhaps dollars aren't a thing anymore - the last people holding dollars are the greater fool. (Note I still hold dollars and ETFs and conventionally safe investments, that's not a knock on the dollar.) But over a long enough timespan, there's a greater fool. There are just a lot of people along the way who got a lot of value out of dollars.
Another extreme: There are things like beanie babies where there is a very short amount of time to find a buyer, and the last one to buy the beanie baby before the fad stops is the greater fool. This is over a much shorter timescale, and there are only a few people who get a lot of value out of beanie babies.
Crypto is somewhere in between. I think the black market use case means crypto is closer to the dollar side of the spectrum than the beanie baby side of the spectrum. I think there's a decent chance there is always a greater fool in decades, well long enough for me to get out while I've gotten value out of it.
I'm curious how true is that in practice? I get that there can only be so many Bitcoins (for example), but if there can be infinitely many different coins AND no consensus on what THE coin is, then how protected is the value actually?
(Some) crypto is a deflationary store. There are not many deflationary stores, and the ones that exist (like precious metals) either require a lot of effort to store and secure, or you hold a claim on some precious metal somewhere and not the thing itself. Lots of people want a deflationary store, especially in a time when inflation looks like a fact of life!
Crypto has no inherent value, unlike precious metals. It can (and depending on the crypto, often does) go to zero. That is a risk of the currency. However, if I were to buy a claim on precious metals, I would still have the risk of going to zero (maybe if things really go sideways, no one wants to honor my claim to the metals?)
Crypto will not be useful as a currency for everyday transactions, it is useful only as a thing to hold and store, or useful as a part of black-market transactions. I don't want to make any black-market transactions, but I do want something deflationary to hold and store.
So the target market for crypto you're missing are people:
* Who want a deflationary asset
* Who are comfortable with the idea that the actual trading activity attracts a lot of criminals, but don't intend to do anything criminal themselves
* Who view the risk of a Bitcoin or Ethereum going to zero about the same as their contacts for gold going to zero in a true financial crisis