To the interviewee every question might sound idiotic.
"Why should we hire you?" or "What are some of your weaknesses, or where do you feel you could improve your skills and qualifications in regards to this position?"
I'd ask this question for two distinct reasons:
1. I'd like to genuinely know what the applicant thinks differentiates him/her/ it from all the other smiley faces.
2. I'd like to see if the challenge to the noggin will be enough to make the person talk me out of hiring them.
Many people have managed #2 by starting to brag and show personality traits that clearly raised a flag.
Especially when placing a woman (note-taker) on the table or having more than one person ask questions, you can see how easily someone gets nervous or intimidated. Incredibly funny, especially if your note taker looks hot and just scribbles smiley faces on a blank piece of paper throughout the whole interview...

Every response equals a smiley face.
Remember, the reason you're sitting for an interview is that the employer is intrigued/ tempted to hire you.
We used to have a "scenario questionnaire" that could be used to differentiate the dumbos from who we'd like to hire.
The
"If => Then" style question (answered in full sentences) game is cool, as it shows if people tend to over-think or bolster their responses in order to make themselves look better.
When you dig deeper, you'll find discrepancies on a resume or expose downright lies or fluffed up titles.