Being "punished" for your sins of each life by being reborn and given another chance to make things right. When you reach that state you are no longer brought back but reach Nirvana...a state absent passion, hatred or delusion.
What you sow in each life you reap in subsequents lives. Some I expect never reach Nirvana because they are unwilling to admit they are imperfect. Others are faster learners and reach a state of being that most of us can only dream of reaching.
So whatcha think?