[quote=KaBling]Seen it.Wait, why do we need to delete our Pokemon?[/quote]

Pokemon can't be moved from one game to another without trading. So something, let's say, a bunch of Patrat. needs to be sent to my game (which will then be erased) to get the handful of Pokemon out. It's simpler if you're a breeder or often Wonder Trade, in which case you'll have boxes full of unnecessary duplicate Pokemon.