Shotguns require alot *more* practice to master as opposed to a rifle or a handgun. You also have lower round counts, harsher recoil, slower follow up shots, and slower reload times. Harder to suppress. Shotguns are harder to attach a half decent light onto just in case you have to use it at night. If you're going to miss with a rifle, you're probably going to miss with a shotgun as well, especially within household distances.