>>58665694Regional Pokémon, at the end of the day, are new Pokémon that can add more to their ecological niche; Mega Pokémon are just temporary forms that don't contribute anything to their world, like that movie with the drugged bear. It remains an exceptional case in an individual, but it doesn't contribute anything to the species.
In fact, I think that's the main problem with Mega Evolution: Pokémon are treated more like characters and less like a species.