I watched my brother playing FFXIII and he explained how there were no character levels, only the Crystarium. So when I started a new game, before the Crystarium tutorial there was no mention of CP and I assume I wasn't earning any. I actually felt like I wasn't getting anything from these battles.
Is there any reason to fight these early monsters? Are they tied to some hidden achievement/trophy down the line?
EDIT: The question was initially about Chapter 1, but it should also apply to Chapter 2 where you still get no CP and enemies are more easily avoidable.