The back wheels are smoking more because they’re being driven by the engine and are spinning against the ground, while the front wheels aren’t doing anything except rolling with the car.
I agree that it’s not super realistic, but the game does have to diverge from reality at some point and this is the point I chose. It’d be much harder to get more realistic looking cartoon smoke that still works with this art style. I also think it’s fine like this because it’s very readable - either the smoke is there or it isn’t, and you know exactly when you’re drifting or not.