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It seems like a lot of people are in agreement with you and that's a good question. I find it funny that Fighting is weak to Fairy and while not super effective, Ghost moves can hit them as well. Maybe "Fighting" people just believe more in the energy of the world in supernatural than "Normal" people do. For all I know there could actually be little sprites that work things in our favor and misfortune, depending on their mood, which is why Fairy doesn't do damage. Or maybe adding more resistances would have bulked Normal types more than Game Freak wanted to.
All in all it's just weird speculation that could be answered one day.
no es fake