Actually, if you do have brake failure the best way to slow the car would be to induce a spin and let the tarmac slow you down, rather than a) fly over the gravel in a straight line, like Schumi in 99 (iirc) or b) go sideways at very high speed into the gravel and roll lots of times, a bit like Greg Moore. Gravel is also a bit rubbish in the wet.
The downside is that the tarmac also acts like a get out of jail free card, and so the drivers can make mistakes and get away with them. Having said that, the sheer quality of the driving at the moment means that mistakes are pretty few and far between anyway, so it isn't a big issue really.