[Mawr]

Why wouldn't they? The brake simply overrides the accelerator.

[cardinalfang]

Sportier drivers may wish to brake and accelerate simultaneously (rev matching, weight transfer tricks). Normal cars just cut fuel when braking to avoid two-foot drivers burning their brakes.

[FpUser]

The other use is for mere mortals to simulate differential lock when it is not there. I've used it couple of times.