Because you may have a shot at colleges that previously may not have advanced you to the next round of review, due to your low test scores. Granted, it will help more if you are full pay or a URM.
Personally I think that if it is possible to increase your scores, doing so will keep more doors open. Still, TO will give you an opportunity you wouldn’t have had before. The issue is that you can expect there to be more applicants, as there are a lot of kids with great grades and ECs and low test scores who will also be taking advantage of this opportunity to apply without a score.