Why are shotgun shells made out of plastic while rifle shells are

Seeing that shotguns use plastic shelled rounds, why don't guns generally use plastic shelled rounds? Would it not be cheaper and just as effective? - Quora

What are some military grade shotgun shells? - Quora

Why do shotguns have different looking shells than rifles? - Quora

What were shotgun cartridges made of before plastic existed? - Quora

Why does shotgun ammunition only use plastic cases? : r/Firearms

Is the plastic part of a shotgun casing dangerous if hit? - Quora

Why are shotgun shells made out of plastic while rifle shells are made of metal? - Quora

When were plastic shotgun shells made available? - Quora

Best Shotgun Shells for Home Defense

Why do shotgun shells have brass or steel encasing the base while the rest of the shell is composed of paper or plastic? Is it necessary? - Quora