"What Questions Have We Not Asked"

Recently in interviews I have been getting asked at the end of the interview the following question, "What questions have we not asked that you prepared for?"

After the third time, I am not as thrown off, usually a say I was prepared to be asked "What research have you done on us" or I was prepared to be asked more behavioral-based questions or metric based if they didn't ask them.

For the Hiring Managers here, Why do you ask this question? What are you looking to learn from a candidate?

Other ICs here, How have you answered this question in the past?