You are suggesting that there is an alternative. What perchance might that be? Some authority figure or organization that decides whether something is useful?
The alternative is to say something of actual substance instead of an empty statement saying it's useful because it's useful.
The same can be applied to your comment of "Crypto doesn't really solve a problem that needed solving". That's not an axiom, thats a subjective opinion, saying its not useful because it's not useful. Plenty of people will, and have, argued otherwise.
I didn't say it's "useful because it's useful". It's "useful because it's used by many people". Unless you are implicitly agreeing with me that the definition of useful is that many people use something and find value in it.