It's called willing suspension fo disbelief. I find it very strange the story forces itself to explain the world through mechanics, even when it directly destroys the fantasy it is trying to build. If the world actually worked on game rules, all wizard education would consist of no studying at all, just murdering rabbits until you level up. World built pretending its in-universe rules have to be defined by the game rules is a ridiculous joke. I also think Lord of the Rings would suck if instead of saying "I cannot carry it for you, Master Frodo, but I can carry you!" Sam said "I do not meet class requirements to equip the ring myslef, master Frodo, but I have enough carrying capacity to add you into my inventory!"