Imagine you were put into a car at birth, and the doors were bolted permanently shut. You've never gotten out of the car...you sleep in it, you are always picking up fast food at drive-thru windows. You go to the bathroom in a jar and dump it out the window. :P
You wind up believing you are the car. It was okay for a pretty long time, because you hang out in parking lots and talk through the window to other people just like yourself. But once your car gets old and starts to break down, the odometer is showing a lot of miles...you get more and more depressed about "yourself".
In the meantime, there are pedestrians all around you. You try to avoid them and get on the highway as fast as possible. They look at you in the car and think "how silly". They go to nightclubs to dance, and nice restaurants where they can sit down. These "cars" seem like madness.
Then there is another group of people. They know both worlds. It's kind of hard for them to know who is stuck in a car vs. who is driving it by choice to get around. Also, if someone is walking by they don't necessarily want to say "hey, have you lived in this town all your life and never got a driver's license?"
Note
Remember that there is not a one-to-one correspondence of people to cars. Especially with robot-driven cars:
When the highway fills up with these, it gets tough to go around knocking on windshields saying "hey, anybody in there who doesn't think they can get out??"
A question arises:
"If you were stuck in a car all your life, once someone helps you get the door open and gets you out...why would you ever drive again? Isn't it much better to get rid of your old car and walk around in the world, and dance, and be free?"
You'll probably be angry at whoever locked you in a car without telling you that you could get out of it. That might have been done on purpose. It could have also been an accident. Perhaps the car manufacturer had no idea anyone would ever weld the car doors shut and force someone to do driving errands for them all the time...that might shock them completely! Regardless, you certainly might not feel like getting back in a car and drive around amongst the cars for quite some time!
But eventually, I think it helps you put the car into perspective as a thing that can help you get from one place to another. Also, you might see that there are new ways to look at driving once you can change cars. You might race them--or do engine rebuilds and go to a car show. It just changes your relationship with vehicles. Also you might realize that this process goes further; your "real" body is just a different kind of car.