I don't understand. Why do we need to fix something that is not broken?

HBD doesn't even have utility yet, other than the 20% APR.

Your assumption is this:

Lowering the HBD Apr might people to stake more HP and join in the Governace

But my gut feeling says people will just cash out their HBD to fiat currency HBD -> HIVE -> USD
rather than power up HBD -> HIVE -> HP