Reasons for a 14 year old to drive a backroad with adult supervision?

What are some good reasons for a 14 year old to drive a small (no traffic) backstreet or a parking lot with adult supervision, when they would be getting their permit license in 3 months. Some people think this is a bad idea? Why, they would be supervised and not going fast at all! Reasons to let 14 year olds test drive in a small parking lot or abandoned back street.