“The Brown Bess musket was good enough for your grandpa, and it’s good enough for you! Besides, we have tens of thousands in the inventory, and it’s too costly to switch to a new, unproven design.”
Get some freethinkers who have been there and done that many times and know what the abuses a primary and secondary firearm may be exposed too by your average Mk 1 Mod Ohhhh shoot and scoot Soldier, Sailor , Airman or Marine.
As in .......why do we seek just ONE ?...........:o)
As you well know each environment and each enemy poses a different threat and problems that must be addressed initially and as the threat changes.......When we were dipped we packed the M4 w/ M203, a M1A, a MP5SDA3 and a 12 ga shotgun as well as a 1911A1 or a Browning Highpower in fly away kits and took what weapons we needed when threat briefings were disseminated.
Modern logistics will provide for more than one weapon system IMO for the modern DOD fighting troop !