>>53230342Because pokemon professors are only allowed to have fire, water, and grass type pokemon. And just one of each. And they need to give them to whatever kid moves in next door, or maybe down the street a bit. And if those pokemon add a secondary type after evolving, it has to be a type that that kid could find relatively close to his hometown anyway, rather than a type it would otherwise take him most of his journey to get a hold of. This is basic stuff, man.