Read this:
https://www.fuelexpert.co.za/canirunavgas.php
Apparently the government gets upset, as this fuel has no road taxes. It would be no different than running farm diesel fuel on the highway, which they will hammer you for.
They claim the amount of lead is too high and screws up valves and guides. I'm not sure I buy that, as aviation engines have valves too. On the other hand, air plane engines spend most of their time operating at high Hp levels, and it may burn cleaner, as a result. So, it may be true.
They also claim the lack of light hydrocarbons makes cold starts harder and it does not respond to quick throttle changes well. True airplanes run steady most of the time. Not a lot of throttle changes running through gears. The high compression in aviation engines would allow them to cold start better, but you're not going to start a Cobra in the winter.
They also said the fuel is more dense and would need jet changes. That might be true. Most people are not going to want to use a good wide band O2 to tune it as the lead will trash their O2.