Why in olympic team cycling and point racing does one cyclist every so often move away from lead to the back?

Question

Why in olympic team cycling and point racing does one cyclist every so often move away from lead to the back?

Answer 1

Lower wind resistance through drafting reduces expended effort.

It takes a lot more effort to be in the front of the pack as you 'break' the wind and if you can draft the guy or gal in front of you, you save a lot of energy.

In the team pursuit events you share the workload around whereas in races like the team sprint, the final rider stays at the back until the other riders have pulled off, effectively using the least amount of energy before the final lap sprint.

Answer 2

its to share the work load. the front cyclist is hit by the most wind resistance and must use more energy against the drag. then he/she will drop back to the rear to rest then the next etc.  

Answer 3

Because it is only the top three who actually record a result.