I've seen guys hop and skip a bit as they slow from 'at least a walking pace' to a trackstand at the end of the first lap. The hopping and skipping is unnecessary at the speed they're going and is probably done to provide an incentive for the following rider to take the lead position. As far as actual skidding like the hipsters do, if you're actually running a good ($$$) track tire you'd likely wear through it in one try. Kaboom! Also, a skid will send the rear wheel DOWN the banking, putting the skidder in a rough spot when it's time to go again.