Knives are great, love me a good knife.
Invest a couple hundred million into the development of a rifle, all to accomplish the same end goal you can achieve using a sharp piece of metal as long as my index finger.

What's the purpose of combat? It's to find a way to bring significant harm to the shit the lies beneath a person's skin. There's no more efficient manner of doing that than a knife; just a straight up piece of small, sharp metal that you can hold onto.
One jab to the neck, probably dead.
One jab to the inside of the leg, probably dead.
One jab between their ribs, probably dead.
One jab to gut, probably dead.

Whenever I teach knife combat, I always like to emphasize that you should avoid getting into a knife fight with someone who also has a knife. As the saying goes, in a knife fight the loser dies in the street, the winner dies in the ambulance. Never be equivalent or disadvantaged with the range/reach of your weapon, always be superior.
As a weapon, a knife is meant to be used during an ambush when you have the advantage, when you can't risk gunfire giving away your position, or as a last resort. But I wouldn't exactly recommend it as a main weapon for anyone that isn't specially trained, cause it requires getting waaaaaaay too damn close to whoever it is you wanna kill.

Now you arrive at why we issue knives; if something is trying to kill you, and it's waaaaaaay too damn close, you have the tool necessary to stab a few dozen centimeters worth of metal into its eyes or whatever the fuck it has on its face.

Taking this a step further, we decided to also make knives that could be used to peel cannonballs like a potato. Because if you're gonna get into a knife fight, I ain't letting you go in on equal ground.

I want you in the barracks before curfew, and I want them dead in the street with your blade buried up to the hilt in their face.

We’ve got the following classes of knives and daggers, but it mostly has to do with how much it costs to make them. It gets real fun when they’re the highest class but can only be used like two times.

-FrW Nahli Lok-Riveria