You could argue that PoW has natural attrition of validators because ASICS improve over time which gives more opportunity to enter the market, but that is secondary to the high validator requirements.
Solana validator hardware requirements are incredibly high compared to anything else I'm familiar with.
In additional to the Solana validator from my original comment I've also run Ethereum and Cardano validators (or rough equivalents). They use a fraction of the compute required by a Solana validator while providing similar rewards and network function.
Again, in terms of PoS chain validators the hardware requirements of Solana are significantly higher than any other PoS chain I'm aware of - it's not even close.
High validator requirements are a barrier to entry, but Solana has a Nakamoto coefficient (decentralization score) of about 30 (actually more, but this is a couple of months ago) which is more than most - probably all - fast chains.
https://youtu.be/5NDs3Il2J3Q?list=RDCMUC9AdQPUe4BdVJ8M9X7wxH...
Because it takes money to have enough ETH to be a validator and therefore, you centralize. It takes 20ETH to be a validator, and at the height of ETH valuation, that roughly translated to about $100k. Not everyone has that kind of money to stake. Plus, it is well know that majority of ETH or any crypto for that matter is held by a small group of people, which further pushes centralized operations.
> Indeed, a proof-of-stake protocol enjoys many of the benefits, in terms of efficiency, of permissioned protocols; moreover, while it is less centralized than a traditional permissioned protocol, it is not nearly as decentralized as a truly permissionless protocol, such as Bitcoin.
I hear this take often, but I have no idea why it would lead to less decentralization in practice. PoS means that someone needs to transfer you some of the native token before you can participate in consensus, but there's no practical way for a cabal of validators to stop someone from doing that if there's even one person with Eth willing to sell to you. That doesn't really seem different in practice from having to find someone willing to sell you a mining rig.