In an oversimplified nutshell, a lot of banks like to sell their mortgage loans to free up capital to make more loans. They do not do it to benefit us. They do it to benefit their bottom line and their shareholders.
Thanks @Bob Okenwa but then what’s the point of issuing a government backed loan if they would sell it at a discount like a traditional loan to free up capital.
Investors like to know they are buying a "safe" security so getting one backed by the government is safer theoretically than one that is not.