[hdctambien]

It is easier to run behind someone and match their pace than it is to lead a race. It is also easier to run faster for shorter distances. A rabbit is someone that runs a fast pace for less than the full race distance so the real racers can be pulled through the early miles and save energy for their push to the finish.

Races want runners to run fast times, because that makes them prestigious. Runners want to run fast times, for obvious reasons. So races provide rabbits which lures fast runners to those races.