You're not wrong, but that's kind of a plot hole intrinsic to virtually all video games with combat.
In real life, if you go around getting in life-and-death conflicts with people, you are very likely to be killed before long.
Problem is that most games with combat want to let the player kill more than a handful of people, or there wouldn't be much gameplay involving combat.
The ways around stuff like that, if you want to avoid unrealistic survival, requires some pretty elaborate gymnastics or constraints, like "the game can't follow a single character", "the game involves a lot of reloading", or "the main character has some sort of magic ability to reconstitute themselves".
Essentially all video games with combat also don't treat wounds realistically either. You get hit by a bullet or two from a rifle, you probably aren't going to be running around in more-or-less okay shape continuing to fight as normal.
But, I mean...there are the constraints placed on the developers of what's fun to play. Realistic simulations don't necessarily make for good gameplay.