Very good point, HBD is not pegged by fiat but algorithmically by HIVE, it is more like debt, leading to increased inflation during a bear market, to maintain the peg, more HIVE need to be created through the conversion function. While many users believed that the inflation of STEEM was below 10%, it was actually above 20% p.a. in the bear market because of the SBD debt, which was devastating especially in a bear market. Without the haircut rule that limits the amount of HBD and the conversion rate, HIVE would get hyperinflated during a bear market.