"Hmm," said a small voice in his ear. "Difficult. Very difficult. You don't really fit in any house at all!
"Plenty of courage for cheek, I see, but not enough to stand up for many others against your cousin and his boorish friends, eh? Not even enough to challenge the unfair image your Aunt gave you, although you are brave enough when it comes to trying new things.
"Quite a good mind indeed, but it's hardly ever been put to productive use, has it? Aside from the odd bits of cleverness to get you out of work, it's almost brand new.
"There's talent, oh my goodness, yes - and a nice thirst to prove yourself, but the only ambition you've got is to be left to have a quiet, easy life. Hardly very noble."
"No, there's nothing for it lad. The fact you put more effort into avoiding work than it would take to do the job, and despite that you have never had reason to show an ounce of loyalty to anybody, you had better be Hufflepuff!" it said, shouting the last word for the whole hall to hear.
Harry briefly considered arguing, but then figured it was probably a lot more effort than it was worth. Besides, he didn't really have a preference, and what possible advantage was there to convincing a hat he was brave, intelligent, or cunning?
It was much easier to just go with the flow, and probably a lot more rewarding in the long run too.