The difference is that if a miner does nothing, eventually they stop making money regardless of how many coins they have. If a staker does nothing, they continue to collect and collect even more indefinitely with no additional investment beyond running a very cheap node (or just letting someone else host it). Staking is just trivial in comparison, it's apples and oranges.
> If a staker does nothing, they continue to collect and collect
They do, but the supply of the token also goes up, so their share of the supply doesn’t grow as much, and relative to other stakers, it doesn’t grow in proportion at all. It is true that inflation rewards effectively move value from non-stakers to stakers, but nothing prevents most of the supply from being staked, especially with liquid staking derivatives.
> Staking is just trivial in comparison
I agree that staking is, but operating the node is not! Operating a validator is actually more demanding than operating a miner. For a miner, there is no disadvantage in being offline except for the opportunity cost. But a validator has a duty, and will be penalized for downtime. (Granted, the requirements on Ethereum are quite lax — on purpose, to make it easier for enthusiasts and other non-professionals to operate a node.) Operating a validator requires monitoring and maintenance like any other software. Your server will run out of disk space, your node will disconnect if you don’t update the node software in time, etc. Most validators in most of the PoS networks are operated by professional companies with dedicated SRE teams because of this.
For a major staker, are you saying that running a validator is equivalent in work/cost to running a warehouse full of miners? Remember, we're talking about major players, not just some random guy doing this in his closet.
The flip side of this though is that stakers can have their capital burned because of misbehavior. If a staker gets too entrenched and the other folks in the network don't want them around anymore, their stake can be slashed. Proof of work cannot destroy the equipment of a hostile miner, only wipe everyone's equipment out with an algorithm change.