As a HP holder you benefit from this without even interaction with the protocol, so not only the borrowers earn, a HP holder earns without even knowing the system exists in the first place.
This is true. Nowadays Hive Power has an interest rate around 3% APR. People need only to hold it to earn it. I also build Hive Dollar (HBD) savings, which nowadays has a 20% APR interest rate. I currently have 1505.701 Hive Power, and $250.50 HBD in savings.