>>58864651It's because besides being based on the Kansai region more narrowly, more broadly, it's supposed to be based on rural Japan.
From the perspective of a Tokyo kid playing the games, Gens 2-4 are kind of supposed to be a virtual cross-country tour: Johto is rural Japan, Hoenn is the subtropical areas in the south, Sinnoh is the colder, hemiboreal areas in the north.