It is not even for adults ;-)
For games it typcially adds nothing to the game play. There are cases where one can argue that it adds to realism, to set the style and atmosphere etc. Or even make the violence extra outlandish and unreal.
(Gore basically means blood. Lots of it. Not necessarily violence. A murder mystery with a big pool of dried blood would be gore without onscreen violence. And when I think about those Jason Bourne movies, there were some ultra violent close combat fighting scenes, but there was no gore.)