Development of turbos - leading to better fuel efficency/power ratio
Turbos first appeared on aircraft engines and then cars in the '20s, and f1 in the '70s. Not sure if Indy ever allowed super or turbocharging.
The trouble with racing technology is that it is generally produced for lightness/performance, while most road cars are still steel. Bikes use a relatively tiny amount of more expensive to produce raw material, so they can be fancier but still affordable.