It's worth to noting if staking off an exchange isn't really mean you have no risk to lose your coins because you're staking on a centralized pool where there's a chance the pool is controlled by a scam group or hacker is successfully hijacked the pool.
Any kind of staking is centralized regardless you're stake on exchange or pool with your own non custodial wallet.
I think you are wrong. If you stake coins without intermediaries, then the validator you choose cannot dispose of your coins, and even if the validator decides to leave, he will not take your coins. But stakers risk fines and slashes if the validator misbehaves. This is the order in the polkadot ecosystem, so if someone is ready to risk 100% of the coins for 10% profit per year, then he should carefully study the risks.