>>46603686"Instinct" isn't really the same as "wants to", though. I imagine that's more an explanation for why they're shaped like balls rather than an explanation for why the Pokemon stay in them. Otherwise, they would never break free once they'd reached a certain threshold of "weakness".
>>46604038I always thought the official explanation was that Pokemon "wanted" to be captured in the sense that they approach trainers (you're never the aggressor in wild encounters except maybe special cases like the Safari Zone), but also that they're not going to just let someone stuff them in a Ball. They want to be captured specifically by someone strong enough to weaken them to the point where they can't break free.