Even those who do not have direct exposure to cars can probably understand the fundamental concepts from second-hand experience. Cars and car-related activities are ubiquitous within Western culture. Most people who are exposed to cars daily know everything that is significant to know about them by the time they reach adolescence, including a rudimentary understanding of the user interface. By the time a new driver sits in the driver's seat for the first time, they have learned all the background and are mostly concerned with infrequently used safety procedures and practical driving technique. They are not struggling to understand basic concepts like starting the engine or even what an engine is.
Cars have little in their interface that is intuitive.
It may be easy to figure out how to activate the turn signals, but it is not entirely clear what turn signals are for unless you have some kind of experience with other drivers in traffic. To the uninitiated, a turn signal is a blinking light that appears to be unrelated in any way to the act of conducting the vehicle through a turn. In fact, given no prior knowledge of motor vehicles, it's difficult to see at first how a car could move you from one place to another at all, unless you actually saw one moving. Computers are complex devices in a complex environment too. Computers are far from ubiquitous in real life or in popular culture.