Why we do this
Education through entertainment and entertainment in education. What teaches is a question with immediate feedback - sometimes as a quiz, sometimes as an interactive presentation run live. The review by Dunlosky and co-authors (2013) ranks practice testing among the two learning techniques of highest utility, effective for learners of different ages, and Roediger and Karpicke (2006) showed it produces better recall after a week than rereading.
Running a quiz is the fun part. Writing the questions is the work - and that is the work we take off the host.