This answer is a point of view to why question shouldn't be deleted in one click.
1. Authors do not own questions.
Questions have all the effort the users put in order to make it interesting and constructive. Do you really want authors to be able to simply delete it? Think of the people who might do it just because they didn't like the most voted answer. For that reason I strongly believe that a question once asked in the site belongs to the community.
2. Undo button
The current system works as an undo button. Are you sure you want to delete the question? Otherwise, there's no easy way to fix the mistake.