Is there a difference in cost per round? I mention this because, fact is, when the government is supplying its people with a lot of something, cost of use matters. I remember those early 60’s dodges and Plymouth marketed for city and town police work that had two speed automatic transmissions. They were “good enough”.
I suppose the idea is that 9mm is “good enough” and the cartridges are cheap. And if someone is not a marksman, five bullets are better than one really well placed one - when you may be hard pressed to really well place ANY of them.
re: “I remember those early 60’s dodges and Plymouth marketed for city and town police work”
By at least 1965 Chrysler had the 3-speed Torqeflite transmission; in 64 Chevrolet was still using the 2-speed Powerglide ...