At least in Ethereum - - Stakers earn far less then miners since they aren't burning capital to validate. They only need to be paid for their opportunity cost over putting that capital to use elsewhere. - Their stake does not automatically compound. Each validator maxes out at a weight of 32 eth, and it takes 32 to get a new validator going. - Earnings have to be skimmed back to the execution layer in order to be manually re-staked (if there is 32 eth worth). Those earnings then enter the 'dominion and control' of the staker, so at that point taxes have to be paid on that income.

In contrast, mining can drastically improve the return on capital by operating at larger and larger scales so as to get better and better deals on equipment and electricity. That kind scaling doesn't happen with proof of stake.