There's something special about racing in real streets. The 'artificial' circuits have a certain sameness to them. But every race conducted on real streets has a character of its own - Barcelona, Monaco, and now Long Beach.
With tennis, you can go pick up a racket, take a lesson, and understand how much talent and skill it takes to be as good as the top pros. Same with golf: pick up a club. But not many can go out and get in a race car and experience a drive at over 200 miles an hour.