Six years after the OP it's quite interesting to revisit the argument:

The OP still holds IMO. Empirical facts have proven the theory.

So I suggest we face the inconvenient truth:

• PoW Mining serves the sole purpose of decentralization
• Bitcoin isn't decentralized! See the Hashrate distribution among pools and recognize that (at least) BTC.com and AntPool are owned by one company: bitmain. I'd say that's more of a consortium than of decentralization.
• PoW therefore has failed its promise.

So why are we wasting 70TWh/y today?