At first I thought that "the bank is paying interest on the bank account balance. Why Hive should be different?"
But then I read the post.
it encourages movement of HBD from exchanges to wallet savings accounts which lowers the risk profile for users
Other than one or two tests, I currently do not remember using the savings account. I had no reason. But this would give one.
exchanges won’t be receiving interest payments just for holding their customer’s HBD in custody (unless the exchange puts it into a savings account, of course, but in that case it seems likely that they would have to offer some staking reward as part of such a change in order to avoid looking bad in the eyes of their customers).
Why are the exchanges receiving interest payments for holding their customer's HBD in custody in the first place?
This sounds like stealing! The interest payments are belong to the customers, because they own the HBD, not the exchanges.
The exchanges have accounts just like regular users. They get interest for their liquid HBD at the moment.
https://peakd.com/@bittrex/wallet
They already get 3% APR for holding them in liquid; which most people don't realize.
That's between the exchanges and their customers. In earlier days of crypto, all rewards from PoS coins was kept by exchanges, but over time the trend has been for exchanges to offer it as a service to the customers (sometimes taking a cut, but not keeping all of it).