Although it might have seemed antiquated, the combination of firepower, ruggedness, and low price tag resulted in widespread adoption by the United States military. the Citykiller, it uses wood and stamped metal sheets that greatly reduce manufacturing costs, while its design maximizes durability without sacrificing the firepower provided by standard 12 gauge shotgun shells.
Instead of lightweight metal alloys used in eg. The combat shotgun was a weapon born out of necessity in a world ravaged by war and resource shortages.