hbdstabilizer and hbd.funder are supported because all of the rewards are returned and generate a direct profit for Hive stakeholders, generating demand to remove HIVE from the market (dalz quantified this at about 1 million USD a while ago, probably higher now) as well as increasing the stabilization of HBD, which has enormous potential to create value for Hive as @dalz, @taskmaster4450 myself and others have written about numerous times.
Generating a profit for Hive and removing HIVE from the market not only creates value for Hive stakeholders but also, to the extent it increases the HIVE price, increases the pool of rewards being paid out. @hbdstabilizer and @hbd.funder easily more than pay for themselves.
They don't even stop and wonder how 12% savings interests make sense if HBD wasn't stabilized.