They are basically ‘asking’ kart behind them to push.
Funny thing, watching a recent race, one of the competitors (probably one of the best kart racers in the country) was sent out with to much air pressure (father told me he forgot to drop it). After two laps, she was falling like a rock. She began to ‘tap’ her helmet as people caught her….They actually pushed her back up to the karts she was losing ground to. I had to laugh, but the best learn to make the most of a bad situation.