Luna Lovegood did not confront and suffer at the hands of death eaters for Ravenclaw to be a house of smart snobs
Cedric Diggory did not die for Hufflepuff to be a forgotten house of under appreciated witches and wizards
Regulus Black did not sacrifice himself for Slytherin to be condemned as the house from which all evil and selfish wizards and witches come from
Peter Pettigrew did not sell out his long-had friends to Lord Voldemort for Gryffindor to become the golden house wherein no one can do wrong