As technology advances cars are more reliable, more consistent, and tend to require ever less ongoing maintenance and a lot of what they do still need is stuff like changing the oil (which you can do most quickly and conveniently at the nearest drive-through Jiffy-Lube place that specializes in this one service) or replacing the tires (which you can do most cheaply and conveniently at the nearest CostCo while you do other shopping there).

There's no particular reason why we should expect the best firm at selling cars would be the best firm at fixing them. If there's a market demand for a network of company-owned garages, companies will supply that. If there's a market demand for a way to try out the car first, companies will provide that service too. But there's no reason either of these needs to be legally tied into how you have to buy the car. Me, I'd like the option to buy my car just the way I'd buy a computer. Go to the manufacturer's site online, spec it out, make the purchase online, and have the car delivered to my door or someplace nearby that I can pick it up when it's ready.