I don't think they want to play Hooker. Even if Goff got injured and Bridgewater was starting the game, I think they elevate Blough from the practice squad and name him the backup.
Also getting Hooker snaps means he would need to be active. That means three active QBs and one less position player activated. You can start Bridgewater and use Hooker as the backup and Goff as the emergency QB but they want to play the starters.