The games wouldn't be so piss easy if they adopted the anime's battle rules of only using the amount of Pokemon that the opponent has. I.E. If you have six in your party and you fight a trainer that has three, you also only use three. You would only be able to use all six of your Pokemon in 6v6 battles or against legendaries.

They'd still be pretty easy because of the shitty AI, but at least you wouldn't have the advantage of numbers.