The benefit is that you will not need to file a claim with your own automobile insurer in the event of a minor incident resulting in damage to the rental car but nothing else. (e.g. car damaged while parking).
The concern is that filing such a claim will result in higher insurance rates.
An additional benefit is that there is
no deductible for covered damage under this card benefit. However, there may be a significant deductible under your own car insurance, as high as $1000, ofcourse depending on your policy.