Few things in this life are as exhilarating as flying through a turn at high speed on two wheels with your inside knee skimming across well groomed tarmac. The better racers use this third point of contact to provide extra stability through corners, to the point that their knee is actually supporting some of the weight of the rider/machine combo as both tires began to lose traction. By feathering throttle and/or front or rear brakes, a really hot racer can control the sliding, and distribute it as needed amongst these three points of contact to maximize cornering speed.
Digging this out of mothballs brought back many fond memories, despite the fact that I was never one of the real fast guys in the twisty bits. But that's a story for another day...
p.s. - Off the top of my head I can think of three of ASRA's best racers that didn't bother getting their knees down and still dominated the scene - Nyle Schafhauser, Tim Slagle, and Bryan Thompson.