It's empirically untrue - look around the coin market. Sure - 95% of it is worthless, but there are serious competing value propositions. I think this will remain to be the case.
What I meant is that since anyone could start a coin and the threshold is minimal to start a coin by using existing code and start a new chain that only by attacking the weaker chains
a PoW crypto could maintain its value resulting in one triumphant big chain dominating the market.
