>>47116535A human the size of an insect, or a human-sized insect, would be fucking terrifying for the human. I know fairies have magic, but still. It's about a 50/50 toss up as to whether fairies dominate insects or whether they are constantly at peril from being hunted by them, depending on the work of fiction. IDK why game freak decided to side with the interpretation that makes Bug even worse. It's perfectly reasonable if they wanted to assert that Bug is strong against/resists Fairy, but they just didn't want to.
Compared to a human, an insect is this truly nightmare fuel thing, covered in armor, scary eyes, stingers, etc. Plus since Fairy is the Type that is emblematic of little girls, it makes sense they wouldn't like icky things like bugs.