Until I got to high school, almost everything I learned, I learned from my parents, not because my teachers didn't care or were incompetent (some were, some weren't, same as with any profession) but because they had too many kids in their classes and had their hands full trying to keep order.

I think most people go into teaching wanting to make a positive impact and then get bogged down in the lack of funding, politics, overcrowded classrooms, and tug-of-war between school staff and parents. The only reason I'd ask, "Why do you want to teach?" is if I meant, "Why would you want to deal with that?". I sure don't.