It had been a simple, simple question. A natural one, even. One she was surprised she'd never asked before. So naturally, once she'd realised that she'd never asked it, Twilight Sparkle had to do the most logical thing and ask.
In her, relatively speaking, not too short life, she'd always thought that no question wasn't meant to be asked. No answer, no matter how life changing it could be, should have not been given. Truth was a principle above the needs of the individuals, and it was always the right thing to know more of it.
It was in those spirits that she went to Celestia and asked that questions. And once she received her answer she realised she'd been wrong. Very, very, very wrong.