(The fact that you can't buy a car with one click shows how hopelessly behind the industry is.)
Cars are, for most people anyway, the kind of really large purchase that requires a lot more effort and deliberation, not to mention financing, than makes sense to do in one click.
Until someone gamifies car purchasing, so that when I get 10,000 facebook points, I can redeem for a discount at my local GM dealership. Now that would be a great source of leads for car manufacturers.
I would love to decouple the showroom (sitting in the car, test drive, whatever) from the dealership. If a car manufacturer were to create a space were I could spend some quality time with the car without any threat of encountering a commissioned dealer, I would love it.
Then, I can choose where and how I buy the car later. The manufacturer would benefit from this no matter how I buy the car. Keeping these "shark-free-showrooms" stocked with demo cars, coffee, pastries, and branded swag would just be a general marketing expense.
Cars are, for most people anyway, the kind of really large purchase that requires a lot more effort and deliberation, not to mention financing, than makes sense to do in one click.