Anyone because PoW does nothing to force convergence of rough consensus attacks (aka forks or altcoins).  This is because cryptocurreny is inherently non-fungible.  It doesn't matter if you mix inputs to hide sender/receiver; that does nothing to solve the problem. Assumptions go into the white paper that things like the longest chain rule will prevent two coins with the same algo from existing at the same time and that PoW will force convergence, yet BTC and BCH both exist at the same time with the same algo, clearly nullifying that assumption.

You agreed with my example that cryptourrency does not actually have scarcity because Vitalik can create one billion scamcoins in his basement by snapping his fingers then do it again five seconds later.  The fact PoW does nothing to solve rough consensus attacks means proof of work is in the same boat.  It just happens through slightly different mechanisms.  

So called "network effect" does absolutely nothing to force convergence either, because bitcoin has built-in usurious middlemen called transaction validators who want a cut of every transaction.  Since block space is highly limited, the success of bitcoin is it's own worst enemy, increasing fees exponentially and giving it a reverse Schelling point - driving users to OTHER chains to avoid usury fees, compounding the inability of PoW to force convergence even further.