Uh.. they've already _bought_ the car. What percentage of people will return a car due to a little lag when adjusting radio stations?

e-commerce findings from a major retailer are, alas, not applicable to every domain

Consumer Reports has found that the functionality of the in-car entertainment system is the #1 indicator of customer satisfaction. You might not return the car, but you can bad mouth the system to anyone who will listen and purchase a different brand car next time.

Someone may choose to not buy a car after test driving it and experiencing the laggy touchscreen...or after reading reviews by people who did already buy the car.

Lack of performance is an attribute that would contribute to a potential consumer's attitude towards the whole car. It may not have as huge of an impact as it would for Amazon, but saying it has no effect is definitely wrong.

Well he did say Companies, not Auto Companies. There are a lot of companies that make money by having better performance.