There's really no reason to waive it as far as I know. If you find a good reason, do let us know.

<moved to more appropriate forum>

I was advised by many to waive my right when I applied and think it makes sense to do so. It gives more credibility to your recommendation and does not create the impression that your recommender felt pressured to provide overly positive judgements.

Now, B-Schools likely understand that many applicants can still view the recommendation offline based on their relationship with the recommender. But if this is the case, then B-schools have little to worry about anyway since this sort of relationship only speaks to your ability to connect with others.