Many such online quizzes (also: what is your X name, based on your first & last names, birth year, city of residence, etc.) are very thinly disguised deanonymisation / classification systems.
There are 33 bits required to uniquely identify any individual on Earth. Since the userbase of any online service is already a far smaller subset (particularly when looking at active userbases), answering such a quiz (truthfully) is quite likely a way to specifically identify you. Even as little information as residential and work postal codes is effective at uniquely identifying 90% of a population.
The slightly less nefarious use is in classifying audiences for advertisers, though even this can be abused.
There are 33 bits required to uniquely identify any individual on Earth. Since the userbase of any online service is already a far smaller subset (particularly when looking at active userbases), answering such a quiz (truthfully) is quite likely a way to specifically identify you. Even as little information as residential and work postal codes is effective at uniquely identifying 90% of a population.
The slightly less nefarious use is in classifying audiences for advertisers, though even this can be abused.
Information has value. Don't grant it casually.