How NOT to answer the question, “Why do you want to be an investment banker?”

I want to make a lot of money/I want a house in the Hamptons/I want to date models, etc.
Yes, everyone in banking is in it for the money.  Anyone who says otherwise is delusional or lying.  But, you still can’t say it in an interview.

I love working all night…
Yes, you can say you want to be challenged.   But NOBODY likes working on pitchbooks at 3:00 am and you won’t either.

I want to learn how businesses work so I can advise CEOs.
Two issues here.  First, the typical banker knows (a little about) finance but nothing about operations and how businesses really operate.  Second, as an Analyst or Associate, it will be years before you will be advising CEOs, if ever.