One of my biggest reasons why I do what I do, boils down to the challenges that I frequently get to encounter. There is a wild satisfaction to working on a very difficult and challenging task, product, tool, profession, skill, etc. This satisfaction often involves reward and a sense of accomplishment.
Anybody that has interviewed for a job has most likely run into the trick question. Some interviewers like to throw out multiple trick questions all in an effort to trip up the candidate and get the candidate to doubt him/her self.