>>33038104I almost answered this thread before heading off to bed last night, and just kinda hoped someone else would, but I guess no one did.
We get a new butterfly and/or moth practically every generation because
>The concept of Pokémon was inspired by insects>They go through easily recognizable methamorphosisI believe those are the only reasons. But think about it, 'evolution' (which is actually metamorphosis,) is very important to the Pokémon franchise. The transition from a caterpillar, to a chrysalis, to a butterfly, is easily the most widely taught and recognized example of that, due to how distinct it is.
It also fits Pokémon's system of there being no more then 3 stages in an evolution line, and there's also thousands of different, unique species of moth and butterfly to pull from and play with concept-wise. And there's ALSO the fact that Bug type Pokémon usually evolve very early in the game, so letting a new player catch a caterpillar is the perfect way to teach them the mechanics of evolution.
For this reason I'm shocked we don't have more frogs and toads evolving from tadpoles. Froakie should have been one; a tadpole becoming a frog would have been great for a starter pokémon.