What it sounds like you are suggesting is that cryptocurrencies should be equitable: everyone should have the same rights to own part of the blockchain. This isn't necessary for a decentralized, trustless, distributed transaction ledger, nor is it likely ideal. What would be the value or utility of a ledger which absolutely anyone could add to at anytime for any reason? You would need to solve 2 problems: 1) distributing the tokens fairly and evenly among every person living and yet to live, and 2) distributing henceforth unfathomably performant supercomputers to all of these token-holders-jus-sanguinis. Any analysis of either of these would very quickly approach insurmountable problems.
There are fundamental constraints to computers and computer networks that have to be addressed in order for these technologies to exist. They preclude any sort of utopian currency of heaven where everyone wins, just by the nature of our physical universe and today's understanding of computation.
My claim was that the lower ongoing expense of staking is compensated by lower rewards, so that both systems have similar profit for similar capital outlay. In setups where mining expense is almost zero, the higher rewards of mining give it much more seignorage than proof of stake.
Concentration of ownership means a few entities own most of the ETH. Up to a point (where one entity owns all the ETH, and therfore ETHUSD goes to zero), who cares, as long as there are still enough token in circulation to conduct business?
Decentralization OTOH means that no one can prevent me from executing a transaction on the chain.
With POW, these two things are basically unrelated: concentration can be arbitrarily high, I can still transact.
However, IIUC, with the aptly named POS, concentration of ownership brings concentration of voting power and therefore large holders become theoretically capable of censoring transactions ... not great.
And I don't believe there is any mechanism in place to prevent ownership - and therefore voting power - to reach arbitrarily large levels.
4,300 or so FDIC insured banks.
But um I'm not sure it's so different from Ethereum, where a mining node must implement the protocol or else be unable to participate.
But you do need permission, which is implicitly conferred by following the protocol. It's really quite similar to traditional banks, it's just that the protocol is digital/mathematical rather than legal.