Right on red was introduced in the 70s to save on fuel back when cars had massive engines and weren't very fuel efficient. As there are more and more hybrid or pure electric cars on the road, the efficiency gains are going down. And here in Europe most manufacturers seem to be introducing stop-start systems on their new cars where the engine shuts off at stoplights. So in the near future there will be almost zero gains from right on red, but at that point it will be pretty embedded in American culture and will be hard to repeal, even if it does pose risks to other road users aka cyclists.