I’ve been a police officer for over 23 years and have qualified shooting a 18" and 20" 870, with a full stock, from the hip and from the shoulder.
Just like a handgun, during close contact with a suspect, you don't want to produce your weapon to the suspect. Hip shooting keeps the shotgun closer to you and harder for the suspect to get to.
I know someone is going to say, you shouldn't be that close. Well, when is the last time you actually cleared a house with a loaded weapon and a real bad guy inside? If your on the outer perimeter and end up making entry, you can just lay your shotgun down and use your handgun. You want to keep your weapon close. In real life, it does happen.
I'm confident in my ability to hit a close target in the bread basket shooting from the hip. I'm just as confident with targets farther away from the shoulder. We train for all possible scenarios.
We also qualify shooting our handgun from the hip area.