>>58214107
Because G2 is conceptually just a complement, it's not designed to operate independently of Kanto like Hoenn is.
For example, if you remove all connections to Kanto, pre-evolutions and evolutions like Steelix and Scizor don't exist, leaving you with a dex of about 50 mediocre Pokémon and a few good Pokémon like Tyranitar or the legendary beasts.
Even the gym leaders reflect this dependence on Kanto.