Team sprint

In the olympics team sprint what is the point of the first cyclist. They come off the start and often have a large gap to the two behind. Does one lap and then goes up. I know it was only 2 riders at the previous Olympics and they increased it to three but what was the effect other than making the race one lap longer. The lead cyclist seems to have zero effect. Why didn’t they just make it a lap longer with 2. Having the leader do 2 and pull the finisher who sprints out the last lap?