Modern cheats for multiplayer games don't modify local files (or attribute values in memory), since the server validates everything anyway. They're about giving you information that's available but not shown in the game (like see-through walls, or exact skill ranges), or manipulate input (dodge enemy damage, easy combos). Those cheat can run in kernel mode (or at least evade detection from user mode), so the anti-cheat needs kernel mode to be more effective.