If some flaw is discovered in SHA-256 or other parts of the algorithm, like how MD-5 and SHA-1 had weaknesses, overnight the value goes to zero. Or if a basic widespread exploitable bug was found in most bitcoin stacks like Heartbleed, that went unnoticed, boom, value evaporated overnight.

You can based the entire world monetary economy on a single point of failure like this.

Neither do tulips, doesn’t make them “a good unit of currency” or “not a massive bubble”.

But the core point bb88 was making is that it can serve at most one of those two goals: “store of value” and “good for speculation” are mutually exclusive. Something can be neither, nothing can be both.