That’s the crypto market. Each coin is as close to a perpetual ponzi scheme as you can get. The coins won’t be worthless until there is only a single sucker left.
Among other things, transactions are not cheap, as they were supposed to be. The chain supporters are trying to pivot the whole thing as "Store of Value" which it isn't supposed to be. It does not scale. There are better blockchains offering everything bitcoin does and more (Ethereum for one).
Human beings aren't exactly rational - if we were, the modern world would cease to exist, and we'd collapse into a Hobbesian state of nature.
Beyond that, currencies are (in a way) also backed to some extent by the value of the goods and services available to be purchased with them.
So cryptocurrencies can have value of the second type, but if they don't have baseline demand then there's little to stop everybody deciding to switch from one cryptocurrency to another at some point in time, leaving the first worthless - whereas baseline demand makes that extremely unlikely for a currency used in any major country's economy.
The alternative - for someone wishing to transact in an alternative currency and not pay taxes - is to pay foreign or private powers for protection services and then simply not pay the tax. This is suicide in the U.S. because we have a large & well-organized military, but is commonplace in many other parts of the world - and indeed, the U.S. is frequently the foreign power supplying arms and accepting its currency for many of these rebel groups.