While your idea strikes at the realism aspect of the game, in the end it would just add complication. If the devs wanted to include it, they could have done it easily. An apocalypse survivor probably wouldn’t care about the brand of car he or she is driving, or the brand of engine, as long as it ran and got the job done. The main thing with vehicles is to classify them based on the type of vehicle they are, which is simple.
Trucks are called “truck” and cars are called “car” and bicycles are called “bicycle,” and I don’t think many people care about having much more detail.
You’re not entirely wrong to wonder about it, though, being that they have brands for a few guns in the game (which they didn’t need to include), but I don’t think too many people are really thinking in the same train of thought as you, mate.
If you’re a car enthusiast, you might as well mod the code yourself to include it brands for cars, and make it available for other people who felt the same way as you, which I’m sure would be appreciated by other cata-playing car enthusiasts, but otherwise, I don’t think the devs really care too much about it.