So no, it's definitely not only F1 fans. Some people just like to race. No matter the car type.
Very good point and to add to that I think some people may play these games because codemasters F1 games offer more of a racing experience than other games. I hate how games like forza and the vast majority of other racing games out there just throw you in quick little 3 lap races which just encourage bad driving and cut out all of the strategy involved in racing. The codemasters F1 games may not be perfect but they at least allow you to experience strategy. Tyre wear, fuel consumption, pit stops, long races, changing weather etc. I am a fan of F1 but I wish there were more racing games out there that gave you this experience instead of throwing you in a different car every 5 minutes so you can run some more pointless 3 lap races.