[Ah, this one again...well, surely there's no harm done in answering the question, at least.]

From what I understand, most of the Pokémon here do seem to enjoy battling - or at the very least, they're supposed to, given how the world works. But they have personalities, as everyone does; no offense meant to either Ruskin or John, but from what I've seen their personalities are less complex than those of humans...though it's possible that's just due to the language barrier, if we're going to be generous in making those sorts of assumptions.

As for why battles are held, there are several reasons; I think the most obvious is that it's a way to gain power in this world.