I RFB and have no problem putting down decent times. If you know how to drive right you can use your right foot.
Its easier to drive fast if you use left foot though so I understand why most people use left foot in video games. In real life they will be forced to use right foot unless they feel like tap dancing.
On top of that, in real life, if you try to brake hard and have both feet on the pedals your body will be pulled forward into the pedals. The foot rest, or the clutch pedal, can be used to hold your body in position while your right foot applies proper brake and throttle. If you have both feet on pedals that you need to modulate gradually you can find yourself in hairy situations when you add G's.