We've already explained this. The visual, audio and other elements of a game that you don't have to obtain by playing it (AKA, >ALL< but the immersion) are being broadcast to the entire world. The only other reason one would have to buy the game is to play it for themselves if they wanted to. Your car example is bad because the interior of the car doesn't even make it drive-able. What makes it drive-able is the control and what's under the hood. What makes a game playable for most people? Well, you have the graphical whores, the people who are just in it for the story, the people who like the soundtrack, the people who want to experience the story firsthand, and many other groups. You satisfy all but those who want to play it for themselves.
Well let's consider a different type of game for a second - Minecraft. Are graphical whores interested? Nope. Story? Nope. Soundtrack? Possibly, but given how sporadic the music is in Minecraft watching an LP isn't the best way of accessing it - especially since there'd likely be commentary over the top of it.
If someone records themselves building an epic house in Minecraft, who owns that content? Mojang, who built the engine/graphics (assuming a default texture pack), or the player who built the house? Notch has stated that Youtube offered him to claim content on all the Minecraft videos, just like Nintendo, but he decided not to. So according to Youtube, Mojang SHOULD own all the Minecraft videos. In my mind, this is like Adobe claiming to own every image created in Photoshop. Minecraft isn't a game - it's a toy. It's part world to explore, part creative tool. Anything created within Minecraft should belong to the creator - not the guy that made the tool. But a video of someone creating a house is still a video of someone playing Minecraft.
Let's go with something that's less of a toy then - let's take a board game like Hero Quest. If someone records a game of Hero Quest, where a lot of the different monsters, traps and treasures are revealed to the public - cards and figurines that the artists put a lot of work into making for consumers - should Milton Bradley/Games Workshop own that video? After all, the video shows a lot of artwork that you'd otherwise need to buy the game to see. Shouldn't the consumer have the right to record themselves playing a game that they bought and own? If so, then what's the difference between recording a physical game with physical art assets and recording a digital game with digital art assets? It's not as if the digital art is in a format that can easily be ripped and used elsewhere. And if you think consumers shouldn't have the right to record their own property, where do you draw the line? If there's a painting hanging in the living room of a home movie, does the painter now own that home movie?

