Are staking rewards >10% too good to be true?

"If it sounds to good to be true, it probably is".

In traditional finance, that would be any interest rates significantly above the central bank one. For company or government bonds with high interest rates, you will have to expect a significant risk. This is what I use as baseline, also for crypto.

Staking is a bit different, as actual work is carried out by staking and value generated in the form of network security. A few %, slightly higher than major central banks' interest rates seem reasonable (looking at you, ETH).

Now there are a few coins and tokens (of solid projects!) that offer significantly higher staking rewards. Polkadot, Cosmos and others offer well above 10%, sometimes up to 30% (like Juno).

How tf is this not too good to be true? Where is the big catch. In no way this can be sustainable, so I'm very sceptical. Any lending protocol offering this APY would be dismissed as extremely risky instantly, but these staking rewards seem to be widely accepted as safe and sound.

What am I missing? Where is the big downside hiding in Polkadot and Cosmos. Do they have insane inflation to the coins themselves?