It's just not something you had any reason to encounter, and maybe you were off sick if it was mentioned in biology/science lessons.
Now consider it this way: the first time you experienced fireflies, you were an adult, and you could bring a fully adult, science-aware, sense of wonder to that experience.
I'd count it as a win.
I'm thankful I had maturity to simply say "yes, they're in the deer family, native to Canada and Northern Europe".
They were from China where they probably rarely mention reindeer, and only in the context of Santa Claus.
It's no different from a Westerner rarely hearing about tanukis, and only in the context of trickster spirits in anime and Super Mario Bros 3. How are you supposed to know they're real?
Good for you!
Though I think we geeks are more inclined to understand when others have their "Sherlock Holmes didn't know the Earth revolves around the Sun" moments. :-)