Well, Cataclysm is semi-realism, an apocalypse happen in near future - there are laser and flaming sword, but an microwave trap with shrinking ray is just too over-the-board IMO, what’s stopping the player from crafting a shrink gun from those microwaves and process to shrink all the zombies down, saving humanity?
The same can be said about the high fantasy genre, there are orcs, elves, dwarves, undeads… but not flying-six-headed-giant-with-deady-gaze.