Charging based on usage would require you to provide your mileage to the government, a tracker in your car, or some other privacy destroying method. I guess the government could just ask for your mileage and take your word for it, but that isn't reliable.
Car inspections that happen in most states do take count of your mileage fwiw I believe. However I also don't think charging based on "usage" makes sense here. Due to the jobs some people have, you may need to just drive a ton more and roads will need to be maintained either way however much you drive.
It’s coming eventually, once enough of the cars are EVs, flat fees aren’t going to be very viable if they don’t want people to game them. It’s not hard to read an odometer, it is hard to say where those miles were accumulated f you want to be really fare and get tax revenue to the state/place you were driving in.
