We don’t “force” them to do it. This is repeatedly established to be something they enjoy doing. BW even has this as a plot point: N, a young man who is somehow able to understand Pokémon, is initially of the same point of view as you. To his astonishment, most Pokémon outright refuse to abandon their trainers. At first he chalks this up to some form of brainwashing, but over the course of the game he comes to realize that their desires to train and become stronger are in fact genuine. He ultimately decides it isn’t right for him to decide what they want for them, and spends the sequel targeting abusive trainers exclusively as opposed to tearing down the institution of Pokémon training in it’s entirety. >!There’s also some stuff about a bigger big bad grooming him to be the face of Team Plasma while he controls the group from the shadows, complete with strongly implied child abuse. Oh, and the reason the bigger bad wants to “liberate” Pokémon to begin with is so that no trainer can oppose his own team when he goes for world domination. You know, typical RPG stuff!<