I noticed that in the past few years, the 40 is slowly losing favor with civilians and Police/Military. It won't disappear, but it sure went from hero to zero much faster than expected. I have 5 decades of experience with carrying handguns, and have seen many things come and go. The 38 special was the go to gun when I started, and if anyone would have said that most people would not be carrying a 38 back then, you would have called them nuts.
But it's happening again, and unless something happens to stimulate the sale of the 40 caliber, it is destined to take a back seat to the 9mm and 45 in a few years. Many gun makers just don't push, or even make 40's anymore. I don't see why the sudden shift since nothing changed, it was always an overpowered round with a bit more recoil, like the 357 sig, or the 380. But that never stopped people before.
I can say the shooting a Glock 19 vs a Glock 23, the 19 is much easier to shoot accurately for most people.
Now you can argue either way, but it really is true.