There are, it’s just that the MBS that Fannie and Freddie offer are *unofficially* backstopped from default, even though the market assumes they are. Ginnie is explicitly backstopped. So the real issue is a perverse incentive caused by government intervention, which creates an asset bubble…as is tradition. If you’d like to learn more about the nuances of these entities, here’s the latest update from the best person I know on the topic, Alex Pollock.