The question that no-one ever asks in the Pokemon world is why that long-dead illustrious and ethical human being, having created the technology to store big things in very small things, decided to use this gimmick the way he did - storing potentially deadly ferocious animals with magic powers in a little thingy that you can hang off your belt. Because he wanted the power, that's why. He wanted to know the ecstasy of holding five deadly creatures round his waist. He probably got off on that sort of thing, the sick weirdo.