Yeah, I always thought it was because it was unlady-like. But I like the fall guy explanation better. :P
As for some of the comments, it says Castle Valet Derach when entering the battle. Not incuding Caitlin. And that's what he is, a valet, not a butler (they're pretty similar though).
Remember the plight of Bill in the original games? Yeah. Caitlin's had an "accident." Pokémon aren't allowed to serve as trainers, otherwise some of the humanoid psychic types could be trainers.
This is Bulbapedia's explanation. I'm not certain whether it's correct, but it's something.It is revealed that she possesses some sort of psychic powers, and that in the past, she had an explosive temper that would erupt if she lost a battle causing her psychic powers to cause a lot of damage. This may be the reason why Darach fought in her place in Generation IV.
Apparently she gained the desire to battle after watching Darach.
Well... she can clearly battle now. So I guess this thread has served its purpose. :P
And I don’t care if I lose
Because my heroes did too
They shouted court should be adjourned
Because the jury are fools
And the judge can’t decipher his left from his right
Or his right from his wrong