>>30743635Alright I can take a crack at it...
Evolution and metamorphosis (take your fucking pick. It doesn't matter) is about changing a state into a more advantageous form for the environment they live in.
Thus, GAINING new types can unlock new abilities not previously seen and give you new capabilities that let you adapt.
Plus different physical features can "bring out" the potential they had before.
Torchic's legs are stumpy, but Combusken and Blaziken's legs are long, therefore it can now kick better, therefore it becomes fighting type. Togepi grows wings as Togetic and Togekiss and thus gains the flying type.
That's the easiest explanation and probably what's going through gamefreak's head. "Complete lines" are incredibly boring and unfun, and a need for them to exist would rob us of divergent evolutions like Froslass/Glalie, or I dunno...
EEVEE.
