Good to be a Texan
The reason 9mm is used so prevalently is due to the bean counters, its not the best gun for the job but it gets the job done and is cheaper. Same thing with military body armor, the cheapest bidder got the contract and now its been proven the BILLIONS of dollars spent on it were wasted since they don't pass the ballistics deflection test.
Also the DOD has a contract out for a new sidearm in 40 caliber, now whether it not it will go through who knows. I haven't paid attention in a couple years to see how it ended up but it was a reason for the redesign of the xdm to have an active safety.
At the end of the day the most important characteristic of a gun is comfort. If it feels natural and fits your hand good you will shoot good. A bazooka does you no good if you can't shoot it. I can't even begin to count how many people I've seen at the range with horrible posture and technique. My chl class was downright scary, and I actually had to take the pistol away from the lady next to me because she was muzzle flashing me so much right before she was called out in front of the entire firing line by the instructor. Some people just aren't meant to shoot a firearm.
I hear you about some folks just shouldn't own or shoot a gun. I was at the range not too long ago and saw a similar incident with a man and wife. I could tell neither had probably ever owned and or fired gun before, it was terrifying to watch them shoot, limp wristing, horrible posture, the guys hand was visibly shaking before each shot. This was at American Shooting centers, range safety officer eventually gave them some 'advice'...

