>>15598851
It's a gimmick. In real life you have muscle memory for actions you do repeatedly, such as walking, eating, picking up things, and so on. Those are actions you don't really think about, you just do them naturally. If you are trained in a skill (such as a mechanic using tools) you will be able to perform that action without thinking as well, even if a layman would otherwise struggle.
In video games these intuitive actions are abstracted away. There is no reason to move your legs individually, the game just assumes your character knows how to walk and abstracts it away with directional buttons. The challenge is not in the act of walking, it is in using your walking ability to walk around obstacles.
The same goes for gun handling. The game assumes your character knows how to use a gun and the challenge is in using the gun more efficiently than the enemies. It is not in the act of using the gun itself.
But this does raise an interesting point: what if your character does not know how to use a gun? Deus Ex had a very wide aiming range which would slowly shrink as you stand still and take aim. As you keep putting points into the shooting skills the window would get smaller and shrink faster, simulating how your character was getting better at it.
Gothic had something similar: when you start out your character barely knows how to handle a sword, so the animations are slow and clunky, but as you keep investing points into your combat skills the animations would actually change to be faster and more precise, reflecting how your character keeps getting better. He does not simply hit harder, he also swings better.