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You aren't some super hero trying to conquer the world of Pokemon, you're a trainer who has been given a research mission. Researchers don't fight final bosses, they study and learn about everything they research, which in this case is Pokemon. Not to mention catching every Pokemon is the SIDE quest of every game, it's never a requirement to beat the games, because some people don't want to do that, but for the others, the reward is getting all the Pokemon, not some end game boss fight, or a certificate