Maybe, but since I also wouldn't be too happy if they reversed the transaction after taking the car, we both agree in advance that the sale will not be reversible. For the payment, that's done by using cash (and the possession of it), and for the car, also just possession. I give the buyer the opportunity to inspect the car before committing to the sale, and then it is "sold as seen". Unless I committed fraud, the engine falling out from underneath the car will be the buyer's problem, including in law.
It is always possible to seek redress through the courts whether the financial transaction itself was reversible or not, so that's not relevant here. Neither is the fact that to do that knowledge of identity and evidence is required; those concerns also exist regardless of transaction reversibility.
Which is exactly the point of the finality of the transaction. Private party car sales in the US typically are not warranted. The risk of maintenance on a used car is non-zero, and the buyer accepts this risk when buying a vehicle with no warranty.
Both parties to this kind of transaction understand why finality is required, and don't have a problem with it. It's a second hand "sold as seen" transaction. The buyer knows where the seller likely lives. The seller doesn't know anything about the buyer. Neither party typically carry that kind of cash around, so there are two trips to the bank (with their own risks) that could be saved if there were some sort of easier digital equivalent.