They cant replace the rifle or the pistol, and any time or money spent on the first 2 cant be spent on the far more useful second 2. The smg and shotgun are so limited in scope that they are a waste of time. They cant be concealed or used one handed like a pistol can, cant be crawled with or used in really tight quarters like a pistol can, and they lack the AP performance, range, mag capacity, 22 unit, silenced capability, etc of the rifle. So they are mostly just a joke.