Why is this idea that all the six mons in your party are supposed to be for combat treated like fucking God's word and not questioned? You were obviously not supposed to raise six Pokémon for battles, but choose three or four for that, and leave the remaining slots for utility mons, such as the Psi Pokémon with its Teleport move to let you save time going back to heal before you get Fly, a Cut/Flash knower like the Weed Pokémon, a healer like the Egg Pokémon or a Strength/Waterfall/Rock Smash/Rock Climb knower like the Beaver Pokémon. That is how a trainer would realistically use Pokémon when travelling a region, for combat and other purposes, not merely the former.