Welcome to PokéCommunity! Register now and join one of the best fan communities on the 'net to talk Pokémon and more! We are not affiliated with The Pokémon Company or Nintendo.
Beedrill isnt Flying because a pokemon can't have 3 types, and bug and poison describe beedrill better than bug and flying or flying and poison would do. so it's more or less the same thing like why charizard isnt dragon (oh, maybe theres a slight difference: a part dragon charizard would have been way to overpowered compared to the other starters)