Many (perhaps most) pump shotguns have inertia-type firing pins and safeties that do not restrict firing pin movement. The term "drop safe" comes to mind; if dropped or subjected to significant impact the firing pin may engage the primer with sufficient force to cause a discharge.
My defensive shotgun is a Remington 870 12-gauge pump. I keep it with magazine loaded, chamber empty, action cocked, and safety engaged. This is what "cruiser ready" means. To use the shotgun requires that the slide-lock be released, cycling the slide to chamber a round, and the safety disengaged. This may sound cumbersome, but it all becomes quite natural with repeated practice and takes only the blink of an eye to be ready to fire.
Shotguns that are going into and out of automobiles, into and out of closets, under the bed, standing in a corner, or hanging on wall pegs can all fall, drag across obstructions, bounce around. I prefer to always know exactly what the condition of my weapon is the moment I reach for it, never a question in mind about it, just do everything the same way every time.
Hope this helps.