One other difference is that with compound and such (and even more so with centralized lending products), you are lending, and as with all lending there is a potential for default. There is also risk from the smart contract failing (bugs or expoits). These risks might be small, but that's for the investor to assess. The tokens themselves pile on additional risks. USDT and such are centralized and the issuer may fail (and has smart contract risks, too). DAI and such have its own complex smart contracts that may fail or be exploited.

With HBD, you are just getting paid interest by the blockchain itself. There is no counterparty, and no complex smart contracts involved.