I guess it is ALL about the money. New IHRA rules

Crash a car at those speeds you get hurt. Add a cage. So they need to keep the injuries to a minimum. to lessen the medical payments

Crash a bike at High speed your getting seriously injured with a helmet on. the insurance keeps paying your medical
Get rid of the helmet and your dead. One time minimum payment.
I can buy a high 9 second street bike easily for under 10k. A high 9 second street car, such as a Demon or Tesla, is going to run mega bucks. So the cool squirrelly cats can jump on a 9 second bike much easier because of price range, ride it to the track (no experience needed), and fly down the track on two wheels. My point is, swing at a nat, swallow a camel. If a factory car can get into the 9's, then no cage required. I guess the real question is... "why do we build 9 second cars from the factory for the street?"