First reason is that it costs to much. To get a driverless car it will probably cost 100 grand at the most. Most people can’t afford that so that driverless car company will soon have to go out of business because they will not have the money to build the cars so they will have nothing to sell.
Second, it is a danger of society. A driverless car is controlled by a computer and computers are known for getting hacked so if someone hacks the computer controlling that car they can control that car which can lead to crashes